Interesting. So my gut instinct that even 8GB won't be fully utilized until OS/apps are retuned sounds to be true. Another developer had mentioned that Jetsam limits per app to 1GB RAM so I assume the 5GB being quoted is total for all apps?
My bad. if you want please run this and report your numbers. I stand corrected regarding my previous post - memory budget on iPadOS 14.5.x seems to be restricted to a higher amount as previous versions of iPadOS (on the same hardware). I did the factor wrong for the 2020 iPPs.
Only the A9X and A12X have 2 RAM variants, in addition to M1 iPads... And what happens is just what I explained above...(both variants are treated like the lower one).