>>280286707
You are misremembering, Yoruichi said Bankai is usually (not even always) a power increase of between 5 and 10 times, nobody ever looked at Ichigo's Bankai and said it was 10 times stronger. Ichigo's supposed Bankai ability was just going faster by compressing his sword as noted by Byakuya, that's just changing the form of his sword which is confirmed not to be a true shinigami zanpakuto
And no the hollow mask isn't linked to Bankai either, he could use it in "Shikai" too

Kubo also confirmed even Ichigo's clothes weren't real shinigami clothes until he visited Squad Zero, that's when he got a real shinigami sword and a real shinigami shihakusho. Until the final arc Ichigo is just a very confused quincy who has convinced himself he's a shinigami to the point his quincy powers pretend to be shinigami powers, hence the fake shinigami sword, fake shinigami clothes, etc