Now Yasuo Supports

It can be done, but like most off-meta picks he can be easily countered and become irrelevant. This is especially true with Yasuo. His power is strongly tied to his items, and therefore gold. Supports generally are the most gold-deprived champs in the game. Worse yet, he's feast or famine. If he gets behind then all he offers is a few seconds of denying farm every 20+ seconds. And is super squishy.

Yasuo support only works when he can cheese very early game to get an advantage. If that fails, the lack of gold/items makes him useless. Windwall still exists, but there are tons of better support options out there that bring more to the table at that point.

when did they change that?

sure, after he countered the whole bottom lane leaving them behind in farm, making them irrelevant. he just needs to build 1 crit item and he is set, but even if he was behind, he just traded 1 for 2, not a bad deal for a "sup"