For whatever reason Solus have decided not to formally release a new version of budgie desktop at the moment. They have decided to release the Git version of the desktop to its users which contains this capability.
All other linux distros wait until the software maintainer formally releases software via a version change.
I can only assume they are effectively beta testing software via its users and given the number of issues raised since they started this approach I consider it better to have a stable desktop for 18.04 long term release rather than one with quite annoying usability issues.
18.10 being a interim release we can loosen the reigns here and probably will go with a Git release or budgie desktop 10.5 formal release if that is made in the 18.10 time scales.
We will be backporting stuff to 18.04 but only once it is absolutely confirmed to be stable.