I don't see any links to the exact formula. There is some vague stuff about what it claims to do. So you are taking all of the claims of the salesman at face value. I'm looking at the outcomes and saying, you know, I don't agree that's a great metric when KG is considered a far superior Defender to Rudy THIS YEAR.
It seems to do a decent job with putting Lebron, Steph and co at the top, but after that it gets off imo.
Regarding who you are playing against is the age old starters vs scrubs. Does it account for garbage time, how does it weigh against the rating of the opponent? Scoring 30 on Rudy vs dropping 30 on Pleiss in my mind are two very separate achievements. It says it does adjust for each teammate and opposing player, but exactly how. Based on results I say it is off somewhere in that.
Regarding Chemistry. What if you are on Big Als team and its iso ball all the time and you never get set up, then you get a few mins while he is out that you have better chemistry with his replacement, so all of the sudden you are much more effective. Since you spent 25 mins with Al watching him and 10 mins with somebody else, does the formula adjust for that? Sure you got good marks for the 10 mins where you were in the game log, but the other 25 when it was sparse, was that weighted to eliminate the affect of that chemistry?
IMHO it gets some right and misses a lot. Something to take with a grain of salt. I could trust more if we knew the formula, since we could better rule out situations it can't measure.
Thats the full explanation of what it does. It leaves me with many more questions than answers.