Anyone who sells 20+ million is obvious a trader and whatever they say in relation to trading is designed to benefit themselves.
I say things from learning due to my lack of resources. My trading has allowed me to add to my small resources.
For instance if a big trader says they are buying then really they want you to buy fast and quick for fear of missing out (FOMO) and then they are selling into the buys as the price pumps.
If a big trader says they are selling then they are really wanting you to sell fast and often for fear of losing money (FOMO) and then they are buying what you are selling as the price drops.
Often a big trader comes in as an excited newbie or investor and says that xyz coin is great and they are buying as much as possible because the coin is going to the moon. Sound familiar? Often its a coordinated pump team so it sounds more realistic.
Most times its best to buy or sell slowly and not because you fear missing out. Overall you will be better off buying or selling slowly and often rather than trying to catch the next big move.