Since 1 wallet != 1 unique individual; it could be done. The points you bring up are fair, yes. But I'd also imagine if you were able to pull off a $350 million heist, you'd have some sense about obfuscating your withdrawls.
Not to mention, converting your initial crypto tokens into another currency, and then another currency, and eventually making it to Fiat. For example, converting to Monero and back to BTC would be near impossible to trace.
On top of this, there is Paxful which you can utilize for cash payments.
There are many, many ways if you are determined. I don't think anyone would be silly enough to attempt a $350 million withdrawal from Coinbase.