Grapple SM question

[blahpers]

So SM difference affects melee rolls to hit. For example, if Utahraptor (SM +2) attempts to stomp a snake alien (SM -4), my Brawling roll gets a -6 to hit. This is weird, as it doesn't seem to scale well (move Utahraptor up to Amphicoelias at SM +8 and explain how it can't stomp that damn snake without a -12 penalty), but that's another issue that's been beaten to death, and this question is about rules as written.

The rules for grappling say that larger creatures get a bonus when grappling smaller creatures equal to the difference in size modifier. This would give Utahraptor a +6 bonus to grapple the snake with its claws, feet, or jaws (ignoring Born Biter for simplicity's sake).

My question is, do these stack--that is, is grappling considered an attack for the purposes of the first rule? If so, that means that the grappling bonus for size always cancels out the attack penalty for size, and that makes it seem kind of silly to define an effective zero modifier as "+X, then -X". If not, then are there other "attacks" where the large size penalty does not apply?

* On the beaten to death issue, I have a personal opinion: Relative SM shouldn't modify attack rolls at all--it should modify dodge rolls, with dodge being disallowed or rapidly penalized when the cross-section of the attack is larger than a step or two for the target and they aren't on All-Out Defense. Even on AOD, if the cross-section is larger than the target can move in the attacker's turn (a second, unless Altered Time Rate is involved), then nix the dodge. In short: nobody ever has trouble kicking a dead cat.