Probably a storm in a teacup
Really not entirely sure this is quite as big a deal as portrayed, odious as it may be.
Does anyone actually use Mail outside the kind of tablet-based environment that is locked down to Microsoft Store apps anyway? In that context, Edge (and wrappers thereof) is the mandated browser in any case. I suspect that the number of people who this adversely affects on a proper desktop environment with a choice of superior alternatives in the first place, is practically irrelevant.