I find there are 2 kinds of PhD holders in engineering, those who are diligent and capable and were able to follow through on a difficult problem for years; and those whose problem solving abilities are so impractical that they stayed in school for as long as possible.

The first is worth their weight in gold, the second is fairly easy to detect after a few git check-ins.

Actually I lied, there's a third kind, brilliant people that get bored with their job and write super-complicated frameworks to satiate that boredom. That's not restricted to PhDs but I see it more often with them.