You seem to be taking it as given that the size of stuff should match between different displays, but you don't give any reason why that's desirable. I understand the argument for 1:1 WYSIWYG in DTP, but not for UI. I haven't been doing much DTP in the last decade.
Some people prefer larger UI and some prefer smaller — partly due to differences in vision and partly just preference — and today's industry lets them choose. Your proposal takes away that choice and thus is guaranteed to anger people.
First of all, whether or not something offends people is rarely the best reason to do something.
Secondly, "choice" is a generous way to describe it. It's more that sizes are happening of basically their own will, whether the user likes it or not. At least if inch measurements were respected, the designer could be deliberate about a decision. This would not invalidate user stylesheets or zooming; I can't fathom a single disadvantage here.
Some people prefer larger UI and some prefer smaller — partly due to differences in vision and partly just preference — and today's industry lets them choose. Your proposal takes away that choice and thus is guaranteed to anger people.