Kinda shameful that DPI scaling has never been a thing in Linux. I'm glad it's being worked on. I'll keep a Linux install kicking around once Wayland and/or Mir land with this stuff.
It's a really hard problem -- especially for fractional scales where hairlines become blurry (or too wide, or too thin, or inconsistent).
But GNOME isn't doing it the hard way.
It's not a hard problem at high pixel densities. We should be able to just specify the display density in DPI and sizes with device independent units. We've been doing this with print for ages.