I apologize. This is a case where the rules seem like they are more rigorously defined than they actually are.
The official rule for Acrobatics proficiency is "The character gains +2 to saving throws where agility would help avoid the situation." The phrase "such as tilting floors and pit traps" is intended to help the judge visualize what sort of situations those might be. But if the pit trap doesn't afford a saving throw in the first place, a +2 bonus won't matter.
The pit traps detailed on p.240-241 do not afford a saving throw, but have only a 2-in-6 chance of going off. If you invent a different type of pit trap that does afford a saving throw, Acrobatics would apply.
Acrobatics would likely also apply to:
Save v. Blast to avoid bricks from the ceiling
Save v. Blast to avoid portcullis falling suddenly downward
Save v. Blast to dodge a rolling rock
Save v. Blast to avoid a scything blade