I'm so sorry for the late reply! Just to let you know what's going on:
As Carlo wrote in the PR, the icon stuff is on pause because it's a burning hot topic atm. and there's many things to consider.
More info about the heated discussion can be found here, but I can try to boil it down for you:
Gnome upstream wants us to ship their new icons
Not to belittle Gnomes work, but we think the suru icons looks better
Upstream icons are optimized to scale best at 32px. The dock in Ubuntu is 48px
We would like to ship only suru icons but Snaps will keep their original cross distro icon
If we want suru icons, it will be a HUGE task
We are not icon designers - we simply tried to pick up the pieces to move the project along
We (the Yaru team) do not make the final call, Canonical will
So in short, we might go all suru or full upstream or we might do a mix - we don't know atm. Anyway, the icon work is paused for now. It was bad timing of me, to reach out to you - sorry!