It doesn't appear to be in this linked article, but Musk has indicated that he is already in contact with Boeing's lead engineer in this area. I think even by the strictest interpretation of official engineering ethics Musk is doing everything right so far.
We don't know how much access he's had to relevant design documents: it's clear he has had some contact with Boeing (but not how much) and it's clear he has pretty substantial domain knowledge, but I don't think anyone here is in a position to assess whether he genuinely does have enough information at his disposal to have correctly diagnosed the problem.
Launching the whole debate with a Twitter comment announcing he could fix it wasn't smart, irrespective of ethics, because he's inevitably going to be accused of a publicity stunt there. Giving a more detailed explanation of where he thinks the problem might lie to the industry press after discussions with Boeing is rather different, and I don't see any ethical obligation for him not to do that.
