That's cool, and it's good to see work going on in more fundamental building blocks of Linux like Gnome to support mobile and reactive UIs. I always felt like this was the biggest blocker to using a Linux system on handheld devices - having a good ecosystem of open source projects that work for that, and having the ability to pick your own desktop environment and components rather than having to have an "all in one"…
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.