And second, it would let us put a C/PF or PG/SG at SF for a game or two to train out of position instead of doing something more extreme, like having to play a PG at C/PF to, say, train up shot blocking or rebounding. That's my point. If the SF training would be that omnipotent, it would damage the balance (we can argue how much balance there currently is but at least some). Especially if SF training would provide reasonable traing for outside defence and inside defense at the same time many players would choose that training not only for future SFs but for other positions too, making defenisve squads more common and thus unbalanced the game as it is now (and there are theories that defense in BB is mroe trained than offense even now reasulting in lower FG% than managers expected). The same with other attributes if they could be trained more easier for SF than now. It would inflate those skills. I don't want to see a day where whole starting five on many teams are all small forwards.
And second, it would let us put a C/PF or PG/SG at SF for a game or two to train out of position instead of doing something more extreme, like having to play a PG at C/PF to, say, train up shot blocking or rebounding.