Why wouldn't you generalize from Musk to billionaires? The amount of agency and power that billionaires hold is not shared by anyone outside of that socioeconomic class. There is a whole category of things that can be done and lifestyles that simply do not exist for those who are extremely wealthy but have, say, 1/10th of that level of wealth.
Agreed, but the fact that Musk is a billionaire has nothing to do with him giving out hypocritical advice. It's a non-sequitor.
Now in general human beings love giving out hypocritical advice so him being a human is far more relevant than his being a billionaire, at least if our goal here is to talk about his advice and not just use this opportunity to bash billionaires.