A character suddenly having a change of personality is an objective thing. If X character from Y show has a completely different personality between season 4 and season 5, that's something people will pick up on. That said, the Hans example you gave is DEFINITELY misuse because his entire nice guy persona from earlier in the movie was a lie. Derailing Love Interests isn't something that can happen within 1 installment of a franchise.
Character Derailment is basically an objective trope labeled as Flame Bait because editors piggyback it to complain on minor things, the concept is rooted in observable criteria. Derailing Love Interests probably has some of the same problems but since Romantic False Lead is a thing it's not as toxic.
Comics are just words and pictures. You can do anything with words and pictures.

Derailing Love Interests is currently an objective trope, but its name and description suggest that it's based in Character Derailment, which is categorized as flamebait.
This came to my attention when I was considering the need to remove the Frozen (2013) entry, only to discover it had been removed and readded previously. Myself and the previous remover seem to be of the mind that Hans' character wasn't derailed but merely revealed for what it always was. The other troper sees it as qualifying because the reveal allows for the other pairing to progress.
As with many characterization tropes, there is a lot of potential for subjectivity. This especially true in a medium like film where there's very little time to establish hard characterization to begin with. As such, I think it should be made YMMV.
"Every triangle is a love triangle when you love triangles." - Pythagoras