AML for high-frequency low-value crypto transactions — where's the line?

Still trying to wrap my head around AML requirements for micro-transactions, especially in crypto. If a user is making a ton of tiny $BTC transfers, say under $100 each, but these add up to significant volume daily, at what point does that volume trigger enhanced due diligence, or is it more about the individual transaction size from a practical AML standpoint? Getting mixed signals on this.