We can only speculate, but it would not be surprising if someone was hunting for a reason to get rid of them and thought this was a good excuse. Personally, I don’t think this is a good excuse and while we don’t have all the facts, it sounds like Netflix conceding the therapy factored into the dismissal is probably something they will very much regret admitting to on the record.

If HR policy says no drugs then that’s a wrap. Allowing an employee to violate HR policy probably puts the company in all sorts of legal risks.

isn't this highly illegal, since it is used for medical purpose (mental health) ?

its like firing a person who was sedated by professional Anesthesiologist with Fentanyl during surgery (A friend of mine had a surgery and was administered fentanyl)

It’s illegal, that’s all it is I believe.