What for accounts are these?
Who cares? The bitcoin belongs to this individual. They are free to hold it, move it, sell it, trade it, dump it, anything they want, without any input or interference from third parties. Such is the beauty of bitcoin.
nevertheless kids, its good to understand that there's always people hodling bitcoin waiting for you to forget they have a huge stash they want to unload onto the market
The number of provably lost bitcoin numbers a few thousand at most. There are over 19 million coins in circulation, any of which could be unloaded on to the market at any time. No one is waiting for the market to "forget" about their coins.
Further, moving coins doesn't mean they are being sold.
they're not using bitcoin to buy something or anything.
How do you know that? Perhaps this person has just bought a luxury mansion for $100 million.