I am not sure I can verify this statement, so I will call it an assumption… Many of those are nothing but a FLAC with a quick conversion to present to the customer. So the release is actually a FLAC, and if you want a MP3 320, it will convert them and give them to you. Also, for those that actually know the differences in such files and care about them, I am not sure such a person would ever download anything but the best option available. I would assume they offer such options for those who are unaware of the workings of conversion to lossy formats. If I would want a BandCamp release in MP3 320 format, I would download the FLAC and make it myself… because
- If I want a M4A later, I can easily do that
- I am quite sure I can produce a better MP3 file from the FLAC than the one I would download.
An example of this are the many YouTube converters out there. You can download a YouTube video (or other) to an MP3 and save it on your computer. Thing is, most of these sources are not at all MP3 encoded, but are actually OPUS or AAC within the webm file. So in these cases as well, you are getting a system converted product handed to you derived from the actual source. My point in this statement is only to show that systems automatically making conversions on demand is a fairly common thing.
So, I would call that a FLAC release. But if the same release is at Amazon, I would call that an MP3 release, and in the same, iTunes an AAC release. Then as aerozol has stated, we could (should) have subtypes. Something like a quality identifier (low, mid, high) to show the general quality of the file.
Off topic a bit, if MB would be open to a more significant change, one could add a release (one release) and editors would have the ability to add releases matching the release date, track listing, etc… but you could add references with attributes. So under this single release, I could add iTunes as AAC v256, Amazon MP3 c320, HDTracks FLAC 16bit, etc. This would both provide a less cluttered release group and provide a solid record of the attributes of the individual store front releases.