Interesting difference in the thickness.

Different companies making the chips (GPI/Paulson vs. SunFly) and also different manufacturing techniques:
Paulson = plastic/clay composite that is "squished down" in a compression mold
SunFly = injection molded, with the telltale nibs on the edges where the injection needles were. More like "inflation".

The compression vs. inflation techniques results in the different stack heights. Not noticeable with a single chip, but makes a difference in stacks of 20 in the racks, as you show.

Who knew? (Well, I guess YOU did! )