There is a school of thought that maintains that tuners should not have equalisation or even volume controls - this should be left to the amplifier. The DNT Tune, a Reciva-based internet radio tuner, worked that way - no volume control via the digital outputs, but the analogue outputs could be controlled.
I think it is a bit cheeky of Hama to try to "sell" you this bug as a feature. Whether it was designed into the firmware on purpose, i.e. whether Hama requested it from Frontier, or whether Frontier just assumed it should be so, or whther it really is a programming bug, we shall never know. But it still stinks.
You will have to decide which is the most or least important feature to you - Bluetooth or the equaliser. You can probably still get the older version somewhere (ebay, perhaps).