It should be described so buyers can beware, but it's a personal choice to decide whether someone trust Musk and his estate planning

Technically, it is described. It's described in the S-1. Trouble is that most (active) investors don't read the S-1.

Fund managers and the like do, which covers a lot of passive investors, which is good until a company joins one of the major indices at which points funds may be obligated to buy in.

It's a deeply distressing moment, and I see it as a time to renew calls for consumer-protecting regulations and antitrust laws with more teeth in the markets where this kind of behaviour's currently flourishing.