SA matters maybe 2% on the whole player's season. In this case, it matters about the goals scored from range or direct shoot statistic.

20+ goals aren't a proof of the ability working, to have a clear situation you should see, about those 20 goals, how many were from FK/CK, one one ones where he received the final pass, penalties, headers, and so on, taking into consideration the number of goals scored "shooting from X meters and the ones where you saw player 1 passing to him and him shooting directly, scoring. If those are about or higher of 50% of his total goals scored, then it's a proof it works, else, he'd have scored the same goals anyways. I had for 2 seasons a SS and he scored little to no time, while my current AMC/AMR with no SA scored about 40 goals in this season + the last one. My other AMC/AML/ST has SS sa but doesn't score nearly as much as my role STs.

In the end, it's still preferable to let him play as AM and to use pure STs for the job, unless he gets a blessed season, which happens to a single player time to time.