It seems to be closely tied to 'surreptitious sabotage' and "getting their own back".
The PA person is concealing their resentment and pissed-offness, feels unable to take positive action (being assertive) so takes a course of action that gives them some inner satisfaction they've had the last laugh.
I think it tends to be used in the workplace context, because people are paid to do a job so may feel they can't argue back, so they give themselves the feeling they are back in control by sabotaging (being late, deliberately cocking something up, deliberately not giving someone that important phone message etc).
That said, it isn't unreasonable to extend it beyond the workplace to relationships in general but there is a subtle difference which is why it is often misapplied.
In penelope's post
1- more "two-faced" than PA
2 - PA
3- sounds like they dont want to hurt the person's feeling rather than
PA
4- borderline.... person feels resentful and put-upon, but they arent trying to sabotage, they just dont want to be everyone's servant! But maybe its a bit PA not to put their name on the notice, but may not want to appear to be a "moaning minny" so it's a different dynamic IMO
5- PA
I wonder if the difference in PA and not PA is the intention of the action...