Ethics only matters when there's an effort to enforce it. The Hippocratic oath is just a reason your employer can fire you for making risky decisions. It means nothing if nobody holds you to it.
If you're a doctor working for Neuralink, nobody will expect anything of you but to push the project forward as quickly as possible. For years you only work with monkeys, and when they do finally put a human in the O.R. it's someone who signed away all their rights and accepted all risks to install experimental brain chips. At that moment, that human patient becomes the single most important subject in the entire experiment.
Of course you do it. You're getting paid more money than you ever have in your life to do it, and the entire system is designed to protect you so long as you do what the boss says.