I don't see it as any great advantage in the transfer market. So the advantage would have to come from players actually used.
It would be an advantage if all these clubs' 'B' teams produced the majority of their first team stars, but if you look at the 'top' teams, abroad, the advantage is in the squad players which the 'B' teams mainly produce, & there is nothing stopping clubs in this country from promoting a stronger 'B' team league & putting more emphasis on it, apart from they can't be arsed enough to do it, at the moment.
I very much doubt that even comes into UEFA's thinking. It does however, make City's 'football group' much more difficult to manage.
And that will be the absolute first thing on David Gill's mind, to sell to the cartel, because the other clubs are unwilling to invest enough to match it & it threatens Utd's long term 'global' exaposure, which will be the case with many of the other cartel members.