The album that chaban linked could be a good example. To me it is not clear that we should (necessarily) combine the bandcamp release and the other platforms.
Because the other platforms have a label (‘REDUCED TO THE ROOT’), and Bandcamp doesn’t (“Published by Copyright Control. With friendly permission of REDUCED TO THE ROOT 2021.”). I usually assume more money goes to the artist if you buy from a [no label] source. This doesn’t matter to everyone ofc, but it is a notable difference to me 
Reduced to the Root is Maria’s own label.
(BTW, English version doesn’t mention the year)
It’s a common pitfall to assume “Bandcamp artist account” = “no label”
While Bandcamp has a concept of label accounts with all kinds of features similar to usual platforms (DDEX), it costs extra among others.
So some just create a normal artist account for label activities. E.g. Alfa Matrix or ProNoize
You’ll also often find separate listings on the real artist and “label as artist account”, whereas the label was responsible for the physical release. It having a digital version too is rather a side-effect.
Another question about whether to make multiple or one release: labels can change the title of digital releases. Should we create a new release (with the date of title change as the release date for the new release) in such case?
Also, since the unofficial guidelines in the original post says we should ignore minor differences in release title and follow artist intent, when the cover art shows a different title to the name listed in the online music store, should we follow the cover art title?
I don’t particularly know why Maria hasn’t just put ‘Released by REDUCED TO THE ROOT’ into the Bandcamp text, but with your additional label info I probably wouldn’t bother adding a new release
Care definitely needs to be taken, but also it’s often it’s not the case when it comes to Bandcamp.
Bandcamp is much easier to self-publish, and particularly non-physical labels often don’t care about publishing there (as it’s not a huge money-maker, and it’s not included in the all-in-one systems that usually get used to distribute to all the other channels - and collect stats and collect royalties).
When I release physical media on my label I (usually) insist on having all a release page with all the tracks. If you purchase there the money goes into my hungry little bank account (and then to the artist - but I can’t speak for other labels…). I make separate releases in MB for my releases of this type, also because I have a cat no. for it, and maybe other minor differences.
Similarly, I’ve distributed a few releases to ‘the big streaming sites’ and I would find it weird to have the bands self-release retroactively credited to my label and with the barcode etc I generated. Which is what usually happens in MB when people group digital releases together (someone adds the Spotify link to the bands own Bandcamp release… then later someone adds the barcode and label from Spotify… and we have transformed the self release into something else).
I suspect that text was auto-generated by the distributor “The Orchard”.
Here is another example where it should be even more obvious:
https://uysr.bandcamp.com/album/nuances-ep
Uploaded on the Bandcamp label account of “Underyourskin Records” (artist has his own account) yet says:
Published by Copyright Control. With friendly permission of Underyourskin Records 2021.
Maybe the legalese of other services sheds some light on this?
Album – Nuances - YouTube (originally YouTube Music)
Provided to YouTube by The Orchard Enterprises
℗ 2021 Underyourskin Records
https://www.youtube.com/playlist?list=PLl9PeJUCtE_W0GvzEdFwfTuPnDeNLtS-0
LICENSES
The Orchard Music (on behalf of Underyourskin Records)
(seen on the videos pages)
Re: Release date
Some releases, coincidentally this very EP, are available in advance exclusively, e.g. at a specific service or other means like a code/invite/subscription. Should the date be the regular release date or the earlier one? I’d opt for the regular (“official”) date.
Re. Tracks grouped in virtual “discs”
I’ll let @Eincrou speak: https://musicbrainz.org/edit/97965039
Oh wow, I didn’t realise there was a distro doing Bandcamp! Good on them. Maybe there’s a few others too.
But these seem like exceptions to the rule. In the more common situation of a band doing their own Bandcamp, and the label doing other platforms, it’s incorrect to mark the bandcamp release as being a label release and having the new barcode, imo.