MQA has a possible range of implementations, and I believe that e.g. with MQA-CDs they are really screwing it up.
However, with the current tidal‘s implementation, that is, most content 48kHz and 24bit resolution, first, it‘s better than redbook already because of the resolution (not all 8 additional bits are used to carry the lossy signal), and secondly, adding the lossy unfolded information would at least not harm the main redbook-like part, but would require a much simpler filters with close to none impact already due to a fact that the cut-off frequency is now at 48kHz (assuming only one step of unfold to 96Ksps has been required/performed) compared to 22kHz with redbook content. And I‘m not a bat, I can‘t hear much of a difference even if they do screw the filter at 48kHz, while I‘ll certainly hear the difference if they do it at 22kHz
It‘s as simple as this, from the technical point of view...