BB-Charles once said that SB is shown in "Inside defense" match ratings. Since noone trains it, Inside scoring is always much higher than Inside defense despite ID being at same level as IS. Take a look at these match ratings from last year's finals, for example...
(55784146)Dyionisus's Inside scoring is rated Marvelous (Medium), while Inside defense is Prominent (High). High SB on his inside players would cause a boost in Inside defense ratings, but then his inside players would have 300k+ salary.