as a trope seems to be based on YMMV and duplication of other, pre-existing tropes. The opening sentence of the description is just talking about how you (The Audience) reacts to the events you're witnessing (The definition of YMMV) and when it gets past that in the meat of the article it boils down to: "A moment where shocking events happen and change what was previously the status quo for the worse."
Except that the article pretty mucy exactly describes it as a Wham Episode
(Which already exists). Or Mood Whiplash
(Which already exists). Or Cerebus Syndrome
(Which already exists). In fact, all of these are actually metioned in that article as "related tropes."
It just seems vague and content that is already covered by other, more specific tropes. It doesn't seem to have anything to recommend it as a unique trope.