One of the ways they used to use was called a taxpayer compliance audit.  They would look at everything.  How you lived, what went through the banks. What was reported as income. If your standard of living was higher than what was verified, you had some explaining to do.  A 'properly trained' field agent should ask about wallets and cryto currency.

But since you say it wasn't advice, I'd say you are probably 70% correct at the present time small amounts would not be tracked back as it would not be worth the added expense.