Any PhD worth their salt would know that a much more likely reason why their hard skills were valuable had nothing to do with PhDs and everything to do with them as a person being able to complete a PhD.

This is no different than anyone who spends all their time producing a great album, or building a company or programming a game and I could go on.

The PhD if you want to talk about it in generalized terms has no unique properties that can't be accomplished through other means.