Commercial or not, PD or shareware, native Amiga or ported, that doesn't change the fact they run on Amiga and thus are indeed accountable, versions put aside. As I understand, key question is what fraction of Amiga games require Kickstart 1.2 in order to run flawlessly. Getting exact number od total titles might be quite a challenge. HOL is just a single reference, I can also quote 'Lemon Amiga' with more than 3450 titles, followed by some 2400 at SPS/CAPS and a WHDLoad trailing at 2200. I guess that previous poster meant 21000 floppy disks or something like that. 20,000 games were maybe total count for Sinclair or C64, not for 16-bit machines.
BTW, what is 'buggy' by your definition ? Something that won't run on KS1.2 ?