I ran the test on the Anker battery as well and here are the results side-by-side, if anything the higher margin of error on the Anker will bring that capacity up since when I checked it at 52% accuracy it was much closer to the OEM capacity:
I got the parts in to do an external test to verify these numbers but I can't help but think that these are a pretty good/accurate indication since what I will be doing externally is very similar to what an internal app could
do. I am also still not completely sure that it will work as I want it to, but we will see. At the least, I now have a number in the ballpark so I should be able to tell if it is working or not.