They mystery to me is who is putting fiat in given that it is a relatively shitty place to buy if price is what one cares about?
That's the mother of all questions!
And I don't think it's many people that put fiat in. Hence the long withdrawal delays.
You fail in two ways. 1: The fiat is already there. They don't need more fiat in to process withdrawals. Which is also proven by 2: Domestic JPY withdrawals work fine and EUR withdrawals via SEPA works as it always has. I.e. slow but predictable due to a daily limit.