Apparently, it was for the cybertruck to prevent scalping.
I have read somewhere that the contract would require you to first offer your cybertruck back to Tesla for retail price minus a set fee per mile if you sold it within a year.
Tesla could refuse taking it back, at which point you're allowed to sell it on the free market.
this clause has recently been dropped from new contracts.
Tesla has refused to take back Cybertrucks offered to them, because they can't sell their actual production cars.