While this is technically true, there is a bit more going on.
In the case of a FLAC at “hi-res”, you have no idea where that data came from at all or how it was changed along the way. For all you know, an intern at a music label manipulated it before sending it out to your streaming service. Mistakes are made after all.
In the case of a MQA file, there is a person or entity that has digitally signed the data at some point in time. If MQA authentication passes, you can be sure that the data has not been modified from the point of that signature to the point where it hits your DAC. Of course, what happens before that signature is still open to all kinds of changes. So, who is that signer? Hopefully it’s a trusted source, such as the artist or the label who mastered the content. Their signature is their word that the music is as they intended it to be. MQA authentication makes it possible to detect if anything has been done to the content from that point forward. That’s a better story than the case of FLAC hi-res. Is it fool proof? Of course not – it’s just some entity saying “yup, that’s right”.
Unfortunately, that “signer” is not known by Roon or any other player, because the repository of signers is unknown to anyone but MQA Ltd. I’m working hard to get that repository opened up and made verifiable, but as you can imagine, there is a lot of moving pieces here.
MQA authentication, right now, tells you if someone is saying “yup, that’s right”, but it doesn’t tell you who that someone is… yet.
It’s more than just endorsement. A digital signature gives a recipient very strong reason to believe that the message was created by a known sender, and that the message was not altered in transit.
This is why it’s important to know the signer’s identity in a verifiable manner.
One thing to make note of, is that I am hearing from labels and the MQA team (I have not nor can I verify it) is that more artists are wanting to deliver MQA encoded content to the labels, because they understand this exact issue. The labels are slowly working it into their established pipelines. It’s why you will find MQA content on Qobuz.