The GNOME Calendar maintainers bring up the fact that Linux Mint ships a nearly 2 year old version of GNOME Calendar to its users and still keep the GNOME branding and support links.
The Linux Mint team don't see an issue with shipping old, unmaintained software and would rather ignore the issue and pretend it doesn't exist. The recent releases of Linux Mint have downgraded several pieces of software to their older GNOME 3 versions which re-introduce fixed bugs and removes newer features. This was done to support their theming engine, despite the fact that their theming is already several releases too old for GNOME apps.
In addition, they utilize several old GNOME related system components that apps rely on such as GNOME Calendar so even installing a newer version of Calendar wouldn't be enough.
This ties into a much larger issue of "Long Term Support" desktop operating systems where software can be pulled back for nearly 5 years (or even longer under a contract). Necessary fixes that are too complicated to be patched back in (or count as features) are then missed by users. Users end up using years-old flagship desktops (GNOME and KDE) and get their first impression of those projects from versions that none of the upstream maintainers support.
It's a shitty situation all around: I personally think it's incredibly important to use the latest release of software that's supported by upstream. GNOME does not actively support older versions of its app and shell from more than a release ago and distributions shipping these older GNOME releases can only cause damage to GNOME's reputation.
If this isn't possible, then I don't think it's right to still keep the branding and trademark of the application, much less keep the original support links intact.
It could be better for upstreams to better communicate what versions they actively maintain in a clearer way it's also up to distributors to take collective ownership of the things they use and not to dump them on users who aren't expected to know better. I suspect that the Linux Mint team is going to struggle hard with the GTK3 apps that they now have to maintain in-house when upstream has fully moved on.
Fedora has been the only distribution to me that seems to take this seriously: 6 month release cadence with an extra 6 months of security updates before EOL and software updates are permitted mid-release when they're needed. It strikes the perfect balance between those who need longer term support and also following upstreams.
At this point, it isn't even clear what Mint's purpose is. The thing which made their distribution unique is now an albatross of technical debt. It sounds like they have already dug their own grave.