The amount of BTC OP mentioned is pretty high and I am not sure it is a typo mistake or not but I think OP was trying to say $392,000 worth of BTC.
I wonder if a rich people does not know about basics because it started with how they got that fortune?
If they got bitcoin years ago, with many years in this market, they already knew how to make it right, buying, selling, KYC issues.
To sell that much amount on a centralized exchange is the only option right now, and you can not use all the exchanges as the 12B worth of BTC you are talking about. It will be hard for even an exchange like binance to take on that load. I am surprised to see someone with 12B worth of BTC who doesn't know how to sell bitcoin in the open market and I think the owner of that BTC is in a difficult position right now because his law enforcement authority will hunt him down as soon as they learn about these findings.
Whales don't sell all bitcoins they have with one single order because it can cause a dump in the market. It can create panic that can cause them loss in value of their selling too. In trading and investment theory, they teach us that there is a Distribution phase for whales, market makers to take profit gradually and distribute their coins, stocks to amateur traders, investors.
They must do distributions gradually, over many months and the crowd even don't know that top already touched so that they will continue buying from whales, market markers with belief that market will go up again, will make a higher top.
If you are someone lets say who dont have much that knowledge when it comes to financial transactions or documentations then you would really be ending up on having those kind of questions. We do know that
not all people who become rich do came from gradual process but rather there are some who had made out instant like in lotteries or some pump of shitcoins then it doesnt mean that they are really that
well known on how to make those transactions and thats why they would really be looking like a clown but we cant really totally make out such conclusion considering that not all would really be knowledgeable to that.
On this case then the best thing to be done is that he should really be that hiring some financial advisor or lawyer or whatever that he would really be taught on how things should be done.
On this case which trying to pull out that tons of BTC then it cant really be done with bulks, even on piece by piece and if you are that someone who doesnt have a business, then any huge transactions that would
really come in into such account would really be raising up some eyebrows and would really be definitely be asking on where those funds came from. Its not really that totally shocking.
As for p2p on making transactions then it would really be that too risky since we are talking huge money on here. We cant really just easily make out such transaction without no care.