There are few advertisement networks which are tracking real location. I do not want to mention all those names, I been keeping an eye on them. Just to give you a glimpse of it, all the advertisements on blockchain dot info are always showing ads from real location in whonix workstations(tor browser) whether JS is inactive or active. I tested custom workstations as well, same thing. I tried atleast thousand circuits, same thing. Reinstall gateway twice, same thing.
Then I installed TBB on host tried and the problem was not there any more, I even tried it on AdvOR again no problem.
I think it is a real threat to this project, should not be taken easily.
Tested in VirtualBox and Not tested in KVM yet.