I thought they were quite clear that it is absolutely based on APX 100, but is is not APX 100. So in my mind we should be thinking of it like it's APX 100's brother.
If you stand me next to my brother and look at us it is abundantly clear that 1) we are not exactly the same person, and 2) we are very closely related to each other, probably from the same parents.
I suspect if we were to get two camera bodies with matched lenses (*), and put a roll of SilverMax in one and a roll of real APX 100 in the other and shoot the scene, then develop in the same tank, we would get extremely similar but discernibly different results.
(*) It's a sad comment that I suspect 35mm camera equipment has gotten so cheap that we can easily try this except for the availability the roll of APX 100.
Or better yet, use a step wedge and then plot curves from both films.
"Often moments come looking for us". - Robert Frank
"Make good art!" - Neil Gaiman
"...the heart and mind are the true lens of the camera". - Yousuf Karsh