I have no clue. “TFT” can’t mean “The Frozen Throne”; since that’s not an in-universe time mark.
“The Fall of Tirisfal”? - so, when Arthas came back and wrecked Lordaeron?
'specially confusing since the “official” timeline uses the first opening of the Dark Portal as “point zero”; and that would even make sense in-universe as well.
I can’t even think of any event in recent Warcraft history that could be abbreviated to “TFT” that’s also major enough to be feasibly considered in-universe as the end of one era and beginning of the next.