It's prudent to assume that no skills are wasted on players and that all have benefits. Anything that makes it harder for your opponents to score, eg. shotblocking on a PG, is objectively a good thing.
I've seen other managers advocate OD on PFs (and I'd add passing to that too) and downplay the importance of inside skills on SFs. As time goes by we get a better grip on how the ME goes about processing shots and shot selection, and it continually shows me how well the BBs coded it. For example, in my last game my opponent had a really poor defensive SF and my SFs went to town on him.
So yes, there are a lot of things about the game that the BBs are choosing not to share with us and yes, all skills are useful on all players, for both the reasons you suggest. Better to have it and not need it...