Switching to Creative Mode doesn't activate cheats in the new UI

When enabling the new UI and choosing Creative Mode, the new UI doesn't automatically enable cheats.

How to Reproduce:
1. Go to the Create New Screen UI, and switch to the new UI.
2. Choose Creative Mode.

Observed Result
No warning of changing the game mode and cheats aren't enabled at all.

Expected Result
There should be a warning and the cheats enabled automatically once choosen.