If maintenance grants are turned into increased loans for kids from less well off families (or kids who say they live with the poorest parent) this won’t even save money anyway, since most of it will never be paid back – especially by poorer graduates who are less likely to earn over the c £21 k repaymement threshold.
If anything they should do the opposite and stop means testing adults based on parental income at all, and give the full amount to all students.
c £6000 a year (that’s what loan plus grant was in 2011 outside London when I finished uni, probably a bit more now) with rent often at £3000 a year or more isn’t exactly much to live on (less than a year’s JSA and Housing Benefit for a 25-34 year old in Birmingham), though it’s more than the c £4000 a year students from middle income families get that disappears in rent nearly immediately and plunges those without savings into their overdraft, whose parents often can’t or won’t help financially.
Whilst kids from the very wealthy families often get their rent and even postgraduate degrees paid for, as well as their living expenses whilst in unpaid internships of course. So this is unlikely to affect their privileged position, as long as their families don’t cut them off.