I did buy a new H6 last month.
They’re being realistic because on this forum and another people openly stated they had free replacements every 2 years (to stay inside of 36 or formerly 42 mos).
I do see your point. What Costco should really do is to load test so-called defective batteries. If they fail replace under 36 mos. But the fraud was rampant.
Maybe they would walk the change back.
Keep in mind the below is at 55F, and battery is rated 730 CCA at 0F. The old clearly is not at that.
This is a fully charged 3 1/2 yo Costco H6
View attachment 202206
This is a fully charged brand new Costco H6
View attachment 202207
Imho, the old one may be good based on the tester’s algorithm, but it is in decline.
Nonetheless, at an auto parts store it would not get replaced