Clipping

" This particular record is famously distorted and is intended to sound this way"

+1.  It is pretty rough sounding, in a good way, regardless of pressing.  Lots of overdriven, distorted Bonham for example.  When he comes back in hard on Whole Lotta love it is a lovely mess!  I'm inclined to think you are perceiving the album's distortion as clipping.

The CD doesn’t sound distorted nor does it cause clipping. Obviously playing a guitar with a violin bow causes some distortion but that’s not what you guys are talking about. What causes clipping is unrestrained dynamic range. Distortion per second doesn’t cause clipping.

I love unrestrained dynamic range:)

The LP had the greater dynamic range by a considerable margin. I suspect especially the original Robert Ludwig MASTERDISC issue.

Try listening to Vanessa Fernandez "When the Levee Breaks." It's a 45rpm set of three records of her covers of Led Zeppelin songs. You're even able to hear the lyrics clearly, and she's a fine singer. Lots of the old standards on there. Highly recommended.