The Mazda 30F27 RF tetrode is another valve that was never employed by TV tuner manufactures.
Perhaps it's the same for the American 6CY5 which is also a tetrode specifically designed for VHF TV tuners.
https://www.radiomuseum.org/tubes/tube_6cy5.html
More likely it was decided beam shield triodes such as the PC95/6ER5 and PC97 were better than the RF tetrodes particularly in terms of noise performance.
From the 1960/61 R & T servicing book: Developments in Television Receivers, page 23. A new frame grid triode (PC97)
The presence of this beam shield provides a new way of neutralising the valve which has the advantage that one side of the neutralising capacitor can be connected to chassis, the other side going to the beam plate: see Fig 3. This technique is used in some recent tuners.
DFWB.