Exactly. Unless they have access to MEXC which is highly unlikely, and even then likely against T&Cs. For simplicity sake I assuming you're using the ETH network, but principle applies to BTC, TRON, etc. Try it yourself, when you deposit to NONKYC exchange, you deposit to a personalized address just for you. However when you withdraw it comes from their huge hot wallets which is processing withdrawals for all their customers. You︀ can view all this onchain. Common sense applies; even though a 10K deposit and then︁ a 10K withdrawal 5 minutes later is not definitely linkable between both addresses; switch it︂ up, deposit 10K, withdraw 9K, or withdraw 10K the next day, etc.