64 GU/t is already Tier 2, that’s why a Tier 2 Machine doesn’t “upgrade” the Recipe.
Tier 1 Machines CAN run Tier 2 Recipes when you push them to the Limit, but the Recipe stays as is.
The whole reason this is the case is because the Tier 1 Stuff has an Inclusive 16-64 and the Tier 2 Stuff has an inclusive 64-256, meaning 64 can be both Tiers at the same time.