Actually it's not exactly like that. Computer will try to find the greatest mismatch and exploit it to your advantage. Example:
1. You have SG with great shooting going against opponent's SG with great OD
2. You have SF with good shooting going against opponent's SF with awful OD
Computer will most of the times choose option nr.2.
If your best mismatch player has better driving than shooting, he will make more layups.
But Outside ISO is not all about that - it's mostly a Base offense with mismatches thrown in. You also need better offensive flow for Outside ISO than, for example, Run and Gun. Oh, and you won't shoot much 3s with Outside ISO. You will get much more 3s with Inside ISO. Don't ask me though why.