Seems ridiculous to me. That was the impression I got that they could possibly be limited on how far they could be promoted.
So many issues I can think of with this.
If they are limited on how high they can go, it's going to make a mess of the league tables in years to come.
The big teams are going to have far better B teams than others and will stop other league 1, 2 and conference teams getting promoted, depriving them of much needed income.
In addition, smaller premier league/championship teams with smaller squads may struggle to field a B team of any decent quality and could end up dropping out of the leagues.
Will the B teams really be filled of home grown talent and make that much difference to the national game? If they're that good, they will be on the fringes of the first team, or at least have a number of championship and league 1 clubs willing to give them plenty of game time.
Not sure what the answer is but I'm pretty sure this isn't it.