I would disagree that they don't want to sell. They have put the wall up several times over a few days; at this point anyone that wants to buy a lot of bitcoin would have seen that wall pop up and can expect it to pop up again a few times a day, and they will be able to buy a lot instantly without any slippage. This guy is just advertising his wall, waiting for someone to buy. Putting that wall up so often would be idiotic if they don't want to sell because if the price is undervalued, someone is going to buy a few thousand instantly and that wall guy will lose a ton of money.