So, what value should I change?
I followed thoroughly on the video shown, including the Ctrl + A for Scale (to scale X, Y and Z to all 1.0). Are you saying everyone's Blender size after porting to Substance Painter is different now?
Clearly, it's a bug. I did all the test try and error for unchecking/checking each option, including uncheck/check all the options you mentioned. Same thing.