I don’t think anyone’s suggesting that Microsoft doesn’t know that this loophole exists. Indeed, I think that they do in fact feel like the added subs they get through this mechanism are worth it to them.
But at the same time, I believe they very much intend for the vast majority of folks to be paying the full price.
There may be some crazy black magic marketing thought going into this, in that this kind of loophole is really only known about by pretty hard core gamers, but then those folks also tend to have more influence on the overall gaming community. So having this kind of hidden loophole makes the platform ultra appealing to those hard core folks (especially when compared to the “normal” price), while still having most of the normies paying the normal price.