YES. This is a Time Machine / Finder bug.
<<<< EXTENSIVE TESTING >>>>
I have had the 2.89 PB Available (or similar) on and off for several iterations of reinstalls, clean wipes of HD, reinstall clean image.
The problem will go away on a new install and come back shortly there after.
Uninstalled Box Sync
Thought it was a Dropbox sync issue.
NONE OF THE ABOVE.
When I disable Time Machine and restart ---> I can CLEARLY see that the finder upon opening says 2.89 PB available, followed by a quick "wait spin" icon for about half a second after which the FINDER refreshes and shows correctly that 624 GB are free.
AND (get this...) I can toggle ON and OFF the Time Machine via System Preferences and the Finder will correct itself and then mysteriously start multiplying available disk space.
"Time Machine OFF" is the only solution to correct read of the disk for now.