To weigh in on this debate again....
Age is a protected characteristic like race or gender.
CC will have gone through a process of getting legal advice on whether the policy is deemed discriminatory or not (from a legal perspective). Firms don’t just rush into policies that could them at a massive risk of many employment tribunals. They will have also weighed up the PR risk too.
Firms all have their ways of cutting down application numbers to get to a manageable number of candidates. I suspect that CC have done their data analysis and found this is the best way for them, instead of chucking people out for one spelling mistake or because they haven’t got more than three As at A-level (all of which can heavily impact other forms of diversity). People might not like it, but it might be the most robust way for them to recruit

.
And before anyone jumps on me for this, I personally don’t agree with the policy either, I just know what goes into making a decision like this and that’s usually a lot of considered thought and evidence.