I've seen all the SA icons been activated in live matches (except one x one both ST and GK) but it doesn't mean anything since you miss a lot with SA or score a lot without em.

But if we assume it's effective! How that work? maybe it's adding some points to the involved skill. 4 example CK add some skills to CROSSING and so on, this theory is so defective since you can give the CK SA to DC which his crossing skills deactivated and probably so low. and guess what! it's even working