I don't hang out in OGA much, but your conclusions match up with my assumptions. I also think it's rad to know folks want to see more commercial art assets available. I don't know how to verify my assumptions, tho. The only data I have available to me is my sales (<$300 after a week). I know I'm going to update the asset pack and release a second pack (Castlevania inspired full game art assets seem to be next on the docket), and I think those are good opportunities to sort the licensing issue and/or be confident I picked the right one.
On another note, I am curious what you think about CCBYSA vs CCBY? Edit: I just realized Kenny sells their art assets as CC0 as well, but I'm not sure I wouldn't want to be credited?