This is a bit confusing, because I don't see people in general buying into a "Laurel = PhD" metaphor -- in fact I've only heard the comparison brought up in a fairly negative way -- which is why I thought it was interesting to point out some parallels in a positive way. I don't think the useful parallels are in the specific depth or intensity, but more in the overall "information structure".

Mind you, having achieved both, I have some rather idiosyncratic opinions about the relative difficulty of a Laurel and a PhD, but they aren't likely to carry over well as general guidance.