I think you are absolutely right! I tried Manjaro Gnome with the live environment and the power save feature works, although it only makes the screen go black and not switch it off. I was using Lubuntu before Antergos and it had a nice feature that switched off the screen power after set time.I have tried Budgie and I found several things that just didn't work
You are absolutely right and thank you for going to the trouble. I tried Manjaro Gnome in live environment and the power saving thing works fine there, but I didn't like the interface.The above being said - I took the trouble to install Antergos Budgie over the weekend, in order to get a better feel for your issue.
Under Budgie, the power saving does not appear to work at all.
You are likely aware that at login, you also have the option to choose 2 x Gnome, 1 Gnome Classic and 1 Gnome -Xorg.
I tried the Xorg option and still no joy with power saving.
I already have an Antergos KDE on board, and its Power Saving works fine.