First time for a “trial unban” where they go back to the ban list if they don’t positively impact the format? Yes, this is the first time a “trial” has occurred in the competitive history of the game. The only time they have come close to this was the original ban of High Tide when paper and online ban lists merged.

I’m not talking about unbans in general.

I concur that unbans are usually a reaction to power creep. However, Modern has always been a mismanaged format since it’s inception. The premise of banning the top decks so that Modern was different from “Old Extended” (because Extended at the time became a “Double long Standard” instead of a rotating Type 2 Format) damaged the genesis of the format, which inevitably led to Grixis Twin’s dominance. I do think the format back then could’ve benefitted from Fae/Sculpter/Thopter-Sword/Affinity being legal and providing variance.