> the person giving you their number can also tell you which platform they are on
That... doesn't solve the problem. We don't need fragmented messaging systems, we need the world's largest company to lay down some rules and abide by them. Right now, the existence of iMessage is predicated on the poor performance of traditional SMS messaging. It wouldn't surprise me if the United States (much like Europe's antitrust council) forced Apple to standardize their proprietary alternatives. There's nothing counterintuitive about that to me.
making an antitrust case on the basis of "I don't want to guess" seems weak, but law can always turn out counterintuitive