I thought they have renamed it one day from GTK+ Gimp Tool Kit to Gnome Tool Kit, but I do not find this anymore. Imho Gnome Toolkit would be at least much more appropriate…
From my perspective those things are also pretty political. E.g. Ubuntu ditched Flatpak in favor of their Snap solution. Snap has, compared to Flatpak only Ubuntu’s proprietary store, where Ubuntu has full control over it. So it’s also a fight about influence.
And it’s breaking with traditional standards which people got used to and, as it’s quite new, smaller things need still to be ironed out.