Title sort of explains it. Sketchfab is the only website/app with this error at the moment and I know that my headset is calibrated and my room is all set. However, viewing any 3D model has my headset positioned way above the model.
I found an older unsolved post about the same issue here: Vr headset and controller position very high above the position it's supposed to be. (HTC Vive)
Obviously this wasn’t an issue for long as I’ve used my Vive/Firefox/Sketchfab many many times.
Also I should note that when initially loaded into the model the position is relatively normal (still high) but when teleporting, the position changes further from the floor.