TL;DR: Status ailment imperils are ignored if there are status resistance buffs.

Under previous iteration, if there is a status ailment imperil applied to the unit, then you need both 100% passive resistance and the ailment resistance buff to not get afflicted. However, in the recent GL iteration, you only need the buff to not get afflicted, regardless of whether the unit has the passive resistance. Test was done on both CoW (were it was initially noticed), followed by Lich (both P1 ambush and P2).

This also affects JP. Sinzar tested it in JP with Lich, with similar results. So at some point, JP changed/broke how buff immunities interact with imperils, then were later ported to GL.

Do note that imperil interaction and passive-only immunity is still behaving like normally.