[Kromm]

Sorry, I didn't paste in the common condition in one case when I composed my reply. See the edited version.

The important thing about the spell-like interpretation is that you can call up and put away your Ally repeatedly, at will, until you screw up. The classic interpretation doesn't allow that – if you put away your Ally, he's put away for the whole adventure. This is a big deal because while I'm sure that some GMs don't charge PCs per head on ocean voyages, penalize Stealth for group size, require Climbing rolls from everyone, enforce reaction penalties for 10'-tall demons, etc., most do. Then it's really nice to be able to say, "I stash Demonic Dan until this part is over," with the worst-case scenario being that Dan isn't around for a day or two. But there really ought to be something given in return, or Summonable is too good . . . so "something" here is that Dan shows up for a minute at a time, making him valuable in a fight or for bashing a door, but not too useful as a pack mule or long-range scout.