When attempting to hide a request type in a request type group from the customer facing portal by clicking customize and dragging and dropping it, the request type doesn't get removed and goes back to where it was. I tested this same process in a new project where I created a new request type group with multiple request types and it works on the test portal side.
From what I can tell I don't see any setting differences between the two projects (production and test) aside from the amount of groups, request types, and automations.