Summerends, my impression partly gleaned from hearing the Director of a top flight University talk, was that the main priority is to maintain the world ranking. This is done by recruiting both the best academics and the best students that you can. Yes a desire to unearth some rough diamonds from poor performing state schools, who have the potential to do well and who will provide diversity. But beyond that they seem to be looking for straight intellectual horsepower.
If the French boy were cleverer and thus likely to contribute more I assume he would selected. The number of British students as a proportion of the student body is now quite low in places like Imperial and LSE.
Aside from Oxbridge I dont think many interview, especially for the quantitative subjects. Instead they seem to focus on UMS scores.
As far as I can tell, and purely anecdotally parents of state educated kids feel they are disadvantaged, parents of private school kids feel their children are increasingly discriminated against, and EU parents feel the bar is set higher for their children.
Leaving aside a suggestion that this is because Universities are filling seats with non EU rich but thick. (I suspect instead that international students will be very bright and very hardworking and set quite a fast pace which the others will need to keep up with. ) Instead I suspect that demand for EU places on top courses has risen dramatically. Fees mean that UK students have got more savvy about evaluating value for money whilst the internet and the increasing dominance of English means students elsewhere in the EU increasingly look to the UK for tertiary education, especially in quasi vocational subjects like engineering, finance and economics.
Places seem harder to get not because others are being considered more favourably but because demand has risen.
In parallel demand is sky rocketing at top US colleges. Its a tough world for these kids.
So to get back to the point. Anything on a paper application that suggests weakness is likely to hamper an application for a competitive course simply because there will be better candidates out there.