Upgrading a champ from carousel who already has 3 upgraded items

If you upgrade a champ by taking it from the carousel, and the champ to be upgraded already has 3 upgraded items, one of those upgraded items gets thrown to your bench in favor of the item from carousel.

This is extremely annoying, as I needed both the item (for another champ) and the champ for my tier 3. Why wouldn't the non-upgraded item be thrown onto the bench? I hope this is unintended behavior.