Multiple kinds of PETG?

[VanGoghComplex]

I ordered sticks of 12/8 PETG from ModMyMods. As the days go by, I spend the 2 hours I have a day to myself trying to bend the stuff. It's awful; I'm trashing four out of five pieces, half I don't get hot enough and the other half bubble, it takes almost five minutes of heating them to get a bend in, etc etc. I blow through my stock, having only made one acceptable piece for my loop.

I order more, this time from Amazon because I'm impatient. Same product, it looks like, same brand (Barrow,) but I go to bend it and it gets pliable within 45 seconds. It collapses into a perfect 90° bend with no kink and no flat spots with minimal effort.

The two look identical, are the same dimensions, and are definitely both PETG, but I see they have different part numbers. The brand is Chinese and their website is unintelligible when translated.

I thought PETG was PETG was PETG. Seems like there are different formulations.