My theory was only that, a theory. I don't have any evidence that this is the case. But like you said, it has happened before many times, especially when BTC price would soar really high.
Hopefully, they have few thousand BTC stashed in a cold wallet
I also hope that your theory remains a theory and never becomes a fact because there are already many allegations going on in their name. Many people are directly calling them scammers and making such allegations that they are selling fraudulent services.
Now my point is that they should use it if they have a few thousand BTC stashed in their cold wallet and ensure that users withdraw at the right time.
Otherwise, there is no benefit from all those thousands of bitcoins because scammers also hold thousands of bitcoins in their cold wallets.