I don't think it's wishful thinking, zanzibar. The two schools/parishes I know well used to send a couple of boys a year to each of LOS and the VAughan, and for most of the middle-class boys with ambitious parents that was the expected destination. For the past couple of years, the only boys who have got into either have been siblings or have named the school on their statement of SN. Other boys, even those who you'd think would score highly on all the religious criteria, have not been offered places, even on appeal or by waiting to the end of the summer holidays.
Of those boys, one or two have gone private instead, but the rest have gone to my ds's school. Sure, that's only two or three boys a year who would previously have gone elsewhere, but multiply that across the parishes of north and east London, and it's not a negligible number of boys. The main difference is not that Ds's school will become more m/c (and ironically they could hugely up their m/c quota massively if they introduced a distance criterion, but they are committed to not doing that) but that the school is increasingly being seen as a good first-preference choice, rather than the place to go to if you can't get into cvms or los.
I am in no doubt that that is a positive thing for our school. I have nothing against schools that have a very distinctive ethos and way of doing things (and indeed ds's school has a very strong tradition and ethos of its own) but any system in which some schools are perceived as hugely better than others is, on balance, an undesirable state of affairs other than for the very few who can manage to jump through the right hoops to secure a place. If the Vaughan is as good a school as they make out, then they should be able to do well even with a slightly changed intake.