From my own experience, I would say that the learning is less from the bigger specific teacher assessed grades cohort and more about understanding the enduring impact of changes that were made during and immediately post-Covid @WonkyTree25 .
For us, a lot of these are to do with the physical capacity of the university and our understanding of our space needs and how we can reconfigure things to accommodate more students. Previously, we were right at the limit of our lecture theatres' capacity and would have struggled to take more students as we would have nowhere we could teach them. Since the pandemic we record / stream lectures and there is plenty of space in our lecture theatres for more students because, outside the first week when (in my department) we have to stream some lectures into two theatres, so many of the students don't physically attend the lectures.
Similarly, while this has not happened in my own department, I know that in one of our neighbouring universities, staff are now set up for working from home more which means that they are not required to work at the university as much and so are seen as being able to share offices and conduct confidential meetings online. This frees up office space for the additional staff (many of whom are on fractional contracts anyway) now needed to teach and support the increased number of students as well as for use by university support services, as small teaching spaces for more seminar and tutorial groups and as ad hoc meeting rooms.
Increased digitisation of library resources that ramped up during the pandemic has allowed university libraries to remove even more of their paper resources, creating more study spaces in the libraries, so there is space to match the demand arising from the additional students as well as from the increased number of students who have to live off campus.
Other universities face less space constraints, but may have to make more changes to do with changes in the ability range of their students. There may be some learning there from all the Covid cohorts, as although they weren't less able, they did have less preparation for university-level study and required more support. Some courses, for example, do more 'little and often' assessment to keep students on track, so more students adds a bit more marking time for staff at multiple points in the year rather than an impossibly large increase in marking time at one or two points in the year (although this is obviously bad for staff workloads overall).
From an academic perspective all these changes are not wholly desirable but we have lived with them for several years now and continuing on with them and with more students on some courses is the least bad choice in the current financial climate universities are facing.
While not especially relevant to students applying this year, the bigger picture at many of the top universities is that the increase in numbers overall and focussed on some courses is actually part of an incremental trend of increasing numbers that started with the removal of the numbers cap, so these universities and specific courses within them are always doing a bit of adjusting to having more students than before and are well-practiced in it. This year, these universities were moreso caught out by the scale of the necessary increases not becoming completely clear until well into the academic year, which impacted on the admissions process and the need to accept people with dropped grades, rather than by a general idea that popular course at top universities might be able to increase their numbers a bit year on year by making more offers. There is also the question of what impact the international student levy might have on international numbers in the coming years, how much international PGT numbers might recover with the resolution of some visa issues and how the proposed quality cap in the recent white paper might play out, all of which will push universities towards temporary workarounds rather than big changes at the moment. Similarly, at the university level, for many universities any increase in total student numbers and attendant demand for the library, support services and so on will only be temporary while they teach out the students on the courses they are now closing.