This in turn results in distributions either opting not to track or ship haskell-platform at all (Arch Linux)
Nope. Arch is a rolling release distribution whose policy is directly opposed to the "stable release" philosophy of the Platform. They will package latest versions of everything, not a "stable release". You *cannot* satisfy their requirements with the Platform; ignore them.
There are other rolling release distributions out there for which this does not apply, but our schedule is not relevant to them either; they update when we release. This includes MacPorts, Homebrew, BSD ports/pkgsrc, and IIRC Gentoo portage and the pkg repo for Illumos-based distributions. Each has maintainers who will update the relevant ports/ebuilds/etc. (or no maintainers and nothing we do will matter...).
Fedora, Mint, Ubuntu, etc. --- the folks who do stable releases on a regular schedule --- are close enough to similar schedules that it is worth trying to synchronize with them. As GNOME has, so watching them probably is a good idea.