Understood. And to be clear, I agree with you: there is no evidence that MQA sounds better than even 16/44.1k FLAC, which therefore would suggest that redbook FLAC is equally good sonically to MQA while taking up less file size/bandwidth (perhaps the same in some cases, but 16/44.1k FLAC would be smaller in most cases). Even 24/48k FLAC will be the same size or smaller in most cases than MQA.
RE AAC, I would guess that most (though not all) people could not distinguish it from lossless in a blind text, and of course its data rate will always be smaller than FLAC and MQA.
Finally, RE some MQA files apparently being from different sources or masterings than their FLAC/regular PCM counterparts, yes - there have been reports, and I believe at least some of them have been confirmed, that some MQA releases are based on new/unique masterings and therefore no apples-to-apples FLAC-MQA comparison can be made.