[Polkageist]

Mm, yeah checks out, double pay for a hired goon gets them really committed to the job.

It's definitely not an inaccuracy because the later on in the Dungeon Fantasy splats it's referenced again at that same scale and explicitly indicating +100% loyalty for double pay. Omitted in the standalone DF books because it's probably too finicky for the rock-n-roll style gameplay to fuss about with payroll.

I would note that these interactions don't take place in a vacuum, inasmuch that the GM cares to actualize the hirelings or just let the background chat in the office, justifications, and soothing of suspicions all get tucked in behind the PC statement of 'double the pay'. The blocks in the books for these rules also call out that the hirelings AREN'T robots, and do think about what's being asked of them, and that abuse of that trust goes sour fast. Per the book itself "Remember that reaction rolls are meant to flesh out a situation, NOT to control it!"
Also, though 'Excellent loyalty' mentions that they're willing to potentially die, the word 'potentially' does a LOT of work here. They won't sell their lives cheaply, make poor choices, or become immune to fear and retreat in the heat of the moment. Ok, you could maybe order them to jump into the volcano but that's the sort of thing you get to do ONCE and good luck hiring so much as a dog walker after that.

Would double-pay without justification make a hireling suspicious? Sure! So the GM informs the player "The offer of double-pay has clearly made the hireling worried about why and gives them concern for their safety considering your activities. They respectfully decline the offer and tender their resignation" Fun roleplay. On the other hand, we're dealing with people who are willing to hire on in the first place, know the risks, and are perfectly willing to accept double pay because they're that kind of person.

I'm arguing from the storytelling standpoint that the hurdle of who's going to take money from the PCs to do dangerous stuff for them has already been passed. We're not talking about paying off a shopkeeper to be quiet, or hiring a housekeeper to keep the hideout tidy (though I'll talk about those in a moment). They're motivated by money, and thus at least a passive agreement with the PC's activities, so are already assumed to be operating within the assumptions of the ruleset that more money = more loyalty.

In a modern setting they're the goons with one-bedroom apartments and an distressingly large gun collection. They're the loners that call home on the holidays at best. If they've got a girl/boyfriend it's casual. Young, maybe a little nihilistic, definitely hedonistic, and totally living in the moment. They'll join in something dangerous for the thrill of it and being paid DOUBLE just means they'll have a fat roll to celebrate with if they make it out alive and the thought that they might not never really hits front and center.
In a fantasy setting, it's not that far different. Hardened fighters and toughs, people who know nothing BUT fighting so fighting harder for more money just makes sense. Everyone dies, but if I don't then I'll be two steps closer to retiring than one. Or maybe they fully intend to die with a spear in their hands so double pay means they can party harder before their exit.
That's the kind of person you're hiring for something dangerous, that's the sort of person who answers the call for that job, that's the sort of person who would agree to take any amount of money for this in the first place.

Let's revisit the paid-off shopkeep and house-cleaner. Neither are combatants, neither expect nor are expected to engage in risks beyond their station. A neutral-level shopkeep might cower behind the counter if a fight breaks out in their shop between PCs and bad guys. An excellent-level shopkeep would grab the shotgun under the counter and pop back up to take shots at the bad guys. Will he die? Maybe. But the PCs have paid him enough so that his kid can get braces and tuck some away for college so DAMN if he's not going to something useful. In a non-combat situation the shopkeeper is essentially unbribe-able. For double-pay, you've essentially eliminated all but the most ludicrous counter-bribes and probably still bought a phone call saying "I got paid 3 million to give you guys up. Sorry, it's not personal, here's what I know about who's coming for you. I'm getting on a flight to Costa Rica tonight."
Similarly a neutral-level housekeeper will do their job and keep their mouth shut for most shady things that might be going on. An excellent-level housekeeper will definitely not say anything for even the most egregiously illegal stuff going down and definitely won't succumb to bribes to leave the door unlocked or anything like that.

A final note too about PC's reactions to bad things happening to their hirelings and how that affects loyalty and not only justifies the reaction modifier for double-pay but is called out for a loyalty bonus in its own right. Say the housekeeper gets killed because they didn't give up information to the bad guys. The PC's exact terrible revenge. The next person they hire for the housekeeper may know that it's a little risky, but consider. "I heard what happened to Hector. I also heard what happened to the bastards that killed him. I'll take the job. Even if something bad happens to me I'll rest knowing they'll pay, and my nephew gets to go to college."

All this builds out the tapestry of actions and consequences within the game world. Bad guys will think twice before messing with hirelings, and good help isn't that hard to find if you're willing to pay for it and take care of it.
And all of that can be abstracted behind double-pay = double-loyalty so you can get on with the adventure.