Posting this against myself because it was entirely avoidable and someone else is going to do it next month.
BTC-only checkout, lightning for the small stuff, settled in btc since I opened the account. Fine for two years. Last week a supplier started insisting on a wire, so I flipped settlement to USD in the dashboard to save myself a leg of conversion.
That flip is not a setting. It is an application. Immediately after flipping it the payouts stopped and the account is asking for the full file — incorporation, ownership, a bank in the business name, the lot. $3,260 of settled btc that was withdrawable on Monday is not withdrawable now.
The documentation does say that fiat settlement triggers full verification. I had read it. I read it as a thing that happens when you first set up fiat, not as a thing that reaches back and holds an existing crypto balance.