Have now completed exchanges with Humax Customer Support.
They accept that my observations regarding the Freeview HDR Fox-T2 are valid but advise:
1. There are inconsistencies in data the broadcasters supply to the Freeview EPG meaning not all programmes are correctly identified as SD or HD.
2. The broadcasters have chosen to encrypt everything on their HD channels, including any SD programmes. The Humax then flags all encrypted content as being HD.