Tuck like Stewart defended the relatively few high quality posts they faced. But otherwise, Tuck would guard a myriad of players, some big, some smaller. The exception to the rule is when UConn faced a Jones or Coates. And I'm saying that putting the much smaller, leaner, more perimeter-oriented Gabby Williams in those positions is not optimal or the best use of her skills.
It wasn't Butler because Butler was in no way ready to be on the floor against high quality competition for any stretch of time last year. Which goes to my point in that minus Stewart and Tuck it would be quite helpful if Butler would take the next step and be able to provide those minutes.
For one possession, yes, Gabby guarded Wilson out of necessity due to Tuck's foul trouble. Otherwise they had her trying to defend Omovbioh. When Gabby, Tuck, and Stewart were out there together Gabby guarded Mitchell. Just because she was the best of limited options does not mean it's best for her to play interior post defense. Could she do it better than KLS if needed? Sure, but perimeter defense is where her strength lies and where Geno will want her unless desperate.