~The coding for these investments prevents people from selling the bitcoin after purchase, so investors are left with a valueless investment.
I don't understand the last sentence but taking it with what you're trying to say. It's true that these scam investments coming from tokens, coins and even NFTs, they'll just leave their investors with nothing once they're done with the project.~
What he meant is likely a type of smart contract that is designed to prevent the selling of a token, a kind of the Squid Game smart contract scam. So the smart contract is just coded with a specific address in mind, which is, it's the address of the smart contract creator itself. That specific address is the one that will only be able to sell tokens, every other else can't sell it, but they are only able to buy or move it.
A'right.
I know and understands if he's talking about those smart contracts scam because they do really exists. This scam is quite new and has a lot of victims already.