Yes, that's true (and old).Isn't this 4% thing old news? Or was it never confirmed? Someone here calculated it when they released the new version with %s.
Before you needed 5 skill points per attribute (not necessarily distributed equally) to gain a star. Now you need 20%. So 1 skill point = 4%.
7% is an impressive gaining but I had a number close to this with the old version.Costa gained 7% at (I think, it was around) 128%... that's nearly two skillpoint at old version. I powertrained players incl. season 5 (now I'm 7) at old version, and they never gained at this quality more than 100 with only one pratice match.
With a 4* academy player I sign. He got about +175 in 3 bars practice.
Of course when he became 5*, his gaining dropped to (about) +120.