I don't know if people will be able to see this, but it's a section taken from a FOI request (available to anyone on WhatDoTheyKnow). Someone back in 2018 had requested a list of all qualifications achieved for a candidates (in this case, it's for Geography BA, but there are similar requests for most subjects in other years if anyone is interested). This is just the first I found.
You can see from this that, for those who have them, nationally recognised music or singing qualifications, as well as drama, dance etc are recorded alongside A-levels, including the grade (pass, merit or distinction). D of E is also listed (though this carries no formal UCAS points).
Of course offers will only be conditional on A-level grades and not UCAS points, but I don't think it's correct to say other national qualifications are totally ignored, otherwise why would they be recorded in the Cambridge system? And why would there be specific categories for these qualifications on UCAS if they were totally irrelevant?
Again, there is no need to waffle on about these in the PS. But they do need to simply list them on the drop down menu because they will be recorded, alongside A-levels.