From what I read, someone who sells btc sometimes has trouble receiving the fiats in its bank account. If the sum is large, the bank turns on all its red lights. I guess it's not a problem for someone famous, but for an ordinary citizen, how it happens if he lives modestly, recovers his private keys that he lost 10 years ago and finds himself with millions?
What any whale should be concerned about is the legitimacy of that BTC, if it's not bought/arranged through illegal means, then it's a go. It's, however, not uncommon that banks flag accounts, but it would be for a little while if you have all your proofs provided to them, it's as simple as that.
While some that would want to receive a very huge amount could notify their banks earlier and provide proof to avoid delay. It's all business for banks, they are only being careful of what to tell regulators, and if you are detailed, it's no issue for them.