PureOS is just Debian with a few tweaks. This work is being done as part of the GNOME mainline branch, so any GNOME user is going to benefit from it down the road. And as "alternative" Linux desktops (MATE, Xfce, LXDE) transition to GTK3+, users of these environments will likely be able to make use of it, as well.
Good to see that Gnome are involved in this themselves too, and it's not some Purism fork of Gnome.