I was a bit sceptical, but I have to say that the horizontal workspaces work pretty well. Working with GNOME 40 is both efficient and aesthetically pleasing. And as a side note performance is much better too on Fedora 34.
AFAIK, most DEs place virtual desktops horizontally or in a grid, and I'm actually not aware of any other DEs that dynamically add new desktops as you use them rather than statically defining them up front.