

if there’s additional suspicious activity
Emphasis on this part. Either way, what you’re describing is generally for tax purposes. Going back to the original question of the thread, if I had billions of dollars and wrote a stranger a check, the bank is highly unlikely to make sure I meant it. At most they may report it to the government to make sure I pay gift taxes (which are paid by the giver, not the recipient, and even they apply far above $10,000 but you still need to report it at that level)
Those are all extreme cases unlikely to be relevant to OP’s question.