Say wut? I measured 9 lumens, and I checked the other 2 posted U21 reviews and can't find anything mentioned bout low being way too high. Are you sure you are talk'n bout the stock U21?
9 lumens is fine with me as a low, it's no moon level but that's not what is claimed. They spec'd 15 lumens, so my model tested even lower. Dunno, maybe I had a prototype or something though, so maybe was changed later?
My U21 review: https://budgetlightforum.com/t/-/40242, in OP near the bottom.