Maybe all the signature skills are just a placebo affect, in which we think its doing something but it's just VC badly spent?
Well it can't be all of them because skills like brick wall and closer are easily testable. In blacktop brick wall works for myplayer over and over again and closer shows your stat increase in the pause menu.
I've noticed that since I've removed the Finisher sig skill. I have made more inside shots, contact dunks, dunk in traffic, and drew more fouls. Leading me to believe that the Finisher sig skill is rendered useless in this and is better of not being brought at all.
Just get your Layup, Dunk, Shot Inside & Close, SIT, SOD, Strength, and Consistency up as much as you can.
This is how sig skills have been like in this game
Impressive at first, but really!?