Referring to an earlier comment my DD was told at her interview at Brighton, "You would have known that if you had come to our open day". Oh yes, they know!
But you are referring to a course which interviews. The vast majority of courses don't. Courses which have 1500-2000 applications for 200 places couldn't possibly keep track of who came to open days. In addition, it would be directly discriminatory against those who just couldn't afford the travel costs.
FOI requests make for fascinating reading. They must be a pain in the butt for the Unis though.
I don't think universities particularly care, provided that the data doesn't enter into league tables used by most prospective students. It is deliberate that unistats and league tables list the average points rather than the best 3 A2 grades, to obscure what grades they actually take.
On the other hand, too much information is not necessarily a good thing, unless you know how to interpret it. Universities such as Durham have entry tariffs inflated by the high proportion of students that come from selective (mostly private) schools. This does not in itself mean that their courses are actually "harder" or "better" than courses at universities which take far more students from state schools and have lower entry tariffs. (For my own subject Durham doesn't make the top ten for its course imo.)
Looking at the tables above, I don't know exactly how to interpret them without further information (and I am an academic). Clearly Exeter were not enforcing A stars for English, despite their strange 2 A star offers the following year, but what proportion of those entrants were in any case given contextual offers because of their backgrounds? AAB from one school might well be viewed as an equivalent offer to an A star and 2As from a selective/private school. Getting AAB or lower doesn't necessarily mean that the student will be worse or unable to keep up with the A star students either.
I would want to see how entrance grades on any given course are correlated with demographics and degree results before reading too much into them. At my own university many of the high firsts actually come from students who came in with entrance grades in the lower quartile.
I guess one might try to infer from the above by how much you could miss an offer and still be accepted, but this may well also depend on context (school etc).