Sort of, I believe Fred did discuss RS option with Garrett but ultimately decided not to. He fully realized year on would be a struggle with only 3 scholarship returners an the high level talent cheering on the bench. Garrett went on to star that year after 3 non descript years. In retrospect he would have won a lot more waiting a year but was able to get a short time in the NBA being the man on that team. It was the right choice at the time.
We have to remember there was a lot of question about how Fred's first crop of transfers would work out at ISU. Not to mention the expectation from a lot of people that Royce wouldn't stay at ISU for his sit out year due to his issues and play in Hilton. Obviously he proved the doubters wrong.
I think there is a lot of hindsight in that first paragraph and don't believe redshirting Diante was an option.