I think the point is that additional rounds are poorly representing any sort of measurable return. Maybe the thesis is poorly worded to get attention?
I don't think anything in cryptography should be taken for granted. Any sort of assumptions that were made 20 years ago should be revisited given how much the landscape is changed.
That being said, it actually DOES look like there is a call for less rounds, and I am totally projecting what I think we should be advocating for.
Isn't one of the cardinal rules of crypto "fast crypto is easily broken crypto?"