If you believe that the ultimate is for the husband to be learning (which you obviously do if you’re looking in bmg) then you would want the boy to first be settled in his learning environment and only after he’s had a good schedule for a few weeks, he should start dating. If those are your priorities that’s what you should want. But if you want your sons/sons in law to learn for the sake of fitting in and you don’t believe in the actual value if their learning then you would make fun of the rule and say ‘when they have kids they’ll be too distracted to learn so why not destroy their learning now bec it’ll be destroyed later anyway’.
As for me, I think this whole hoopla over bmg is ridiculous so I make fun of it. Then again my husband is sitting and learning so it’s really the obsession with bmg that gets me rather than the kollel aspect. If you really need a boy in learning, take any of the boys who have expired the freezer (there are plenty to go around) or go to. Any other yeshiva (also of which there are plenty).