Are h2testw results reliable?

Hi! I bought two Kingston 256 gb micro SDs (from different sellers). I was having some issues with the first one so I ran h2testw and it said it's likely defective. I did the same thing with the second one and it also said it's likely defective. I also tried with an 8 gb one and it said it's okay (no errors).

I'm wondering if there's a chance h2testw is wrong, or whether one can always trust it's output. I think it's unlikely I got two fake SD cards in a row. Maybe h2testw is likely to produce a wrong result for bigger sd cards?

Thanks!