However, backing up these kinds of directories has always been ill-defined. Dropbox/Google Drive/etc. files are not actually present locally - at least not until you access the file or it resides to cache it. Should backup software force you to download all 1TB+ of your cloud storage? What if the local system is low on space? What if the network is too slow? What if the actually data is in an already excluded %AppData% location.
Similar issue with VCS, should you sync changes to .git every minute? Every hour? When is .git in a consistent state?
IMO .git and other VCS should just be synced X times per day and it wait for .git to be unchanged for Y minutes before syncing it. Hell, I bet Claude could write a special Git aware backup script.
But Google Drive and Dropbox mount points are not real. It’s crazy to expect backup software to handle that unless explicitly advertised.