many silly people think things like privacy and fungibility is a yes/no 2 option answer. its not... its a % scale or a points system.. where points dont win rewards. but warrants
And how exactly this system works is a secret to prevent people from gaming it. So if you think you can bypass it by splitting your transactions, using proxies, or other methods, chances are you will attract even more attention and will look more suspicious.
When I was withdrawing a large sum of money from crypto exchange, I just took a huge leap of faith, and luckily it all went smoothly. But I was reading reviews and discussions, and other people who use same banks were not so lucky and had their bank account frozen for doing large p2p transfers.
if you read regulations. a custodian/bank/money service has to allow the funds to move unless they are court ordered to not.., they cant just freeze accounts and steal funds.. the most they can do is allow customer to remove/transer balance and close the account.
emphasis banks/custodial services cannot just steal funds as part of their business policy
so when something is just "suspect" but if it meets a certain suspicion threshold, the money still moves but the service sends a SAR to tax office of financial crimes office(depending on reason) where by if there is criminality then a court order is THEN done to request more information and to freeze account
so account funds are not seized for simply moving money(otherwise rich people would have banking headaches each day they buy a lambo)
now the separate situation you experience/heard:
many of the p2p transfers are not frozen due to amounts. otherwise businesses/rich people will have accounts closed all the time
what is actually found is that scammers wanting coin buy coin via p2p. then they call their bank and say that someone hacked their account and spent their money on something the (scammer) didnt want. and request that the transaction is fraudulent. thus red flagging the bitcoin seller as a fraud/thief.. even though it is the buyer being the scammer. where the scammer gets a fiat refund whilst also keeping the coin
this is a known thing called "chargeback scamming" it went rife in the days of localbitcoins which eventually made localbitcoiner sellers have to do their own due diligence by asking for KYC to prove the buyer at the keyboard was the account holder. to protect the seller.
this then made local bitcoin less popular and now people do it via De-fi to avoid kyc.. which is only at the beginning of people doing chargeback scamming. so expect many sellers to see bank problems when chargeback scamming becomes rife on de-fi
and yes many exchanges got red flagged by banks where even centralised exchanges were getting chargeback scammed. which means other innocent people using same cex had a warning to not use that service..
over the last 9 years banks were not anti-crypto as much as said. it was that the chargeback scamming was so rife that anything associated with crypto services that were victims of those scams became headaches. where some banks just said no rather than handling things
(said no to new business account applications where businesses were 'crypto' based)