I am a Peterson fan and frequently reference him in conversation, but I agree - probably not a hill to die on. His message here is correct. Featuring this model on the SI cover is a concerted effort to force "tolerance," and, "diversity," regardless of whether or not one finds her attractive or not.
That said standards of beauty vary from person to person, culture to culture and age to age. It's why we currently have the gentle euphemism, "Rubenesque."
In past eras when things weren't as bountiful as we have them, robust women were viewed as more fertile and desireable.
Quite honestly, when I saw the Japanese model and theSI cover photo, my first thought was the Venus of Willendorf.
I am as well. His comment is spot-on: more purposeful, top-down, politically-inspired manipulation and destruction of standards.
He is certainly used to vitriol, but I imagine he realized - there is a specific young woman at the other end of his comments. She certainly put herself forward and made herself a public participant, but he almost always directs his fire away from individuals (except high-level political actors)