you may note that casting Ulamog, the Ceaseless Hunger, and pausing, per default means “triggered ability is on the stack, I am thinking about targets”.
I don't think that this is what Kevin said. A player is assumed to pass priority unless they explicitly retain it, but AP isn't trying to retain priority here, he isn't required to hold priority in order to place his trigger on the stack. In fact, in AP's world, no one has priority yet because his trigger is waiting to go on the stack.
The tournament shortcut of assuming that AP has no game actions to take is just that - assuming that he will not use his priority unless otherwise specified. It has nothing to do with assuming that triggers are missed unless otherwise specified, missed triggers are handled by the missed trigger policy.
So I'm not seeing a disconnect here - triggers are assumed to be remembered until proven to be missed, and AP hasn't proven that he has missed his trigger until he allows NAP to do something. NAP could say “in response?” or “Ulamog on the stack?” to determine whether he has priority without revealing the nature of his response.
Finally, keep in mind that the reason these seem different is because these are two different situations which are intended to protect two different players from two different things. In the former, we're protecting the game integrity by preferring to have the game proceed naturally (with the trigger in the correct place) until the players prove that this is not possible. We're also protecting the controller of a triggered ability against an opponent who may try to rush them with a snap “in response counterspell, oh and you missed your trigger” as soon as Ulamog touches the table.
In the second situation, we're protecting NAP's right to have the “last word”, so to speak. AP has a large amount of control over how they move through their turn, and it's important to make sure that AP doesn't have even more control than they deserve, for example, by saying “Attack with these guys. Do you have any effects before blockers? No? OK, then I'll tap your team.”, or “Infernal tutor. Any responses? No? OK, then I'll crack LED for BBB.” (The “Combat” shortcut comes from a similar line of reasoning.)
So no, I don't believe that there's a problem here. The policy of “if you don't know where in the turn we are, ask your opponent” or “if you don't know if the trigger is on the stack, ask your opponent” is still entirely true, and of course, if there's any confusion, the judge who responds will be able to determine which of these sections of policies is relevant in this particular call.