Just my view of it, both with Williams and other things, but scale tends to have many meanings, it is in the eye of the beholder. To a rivet counter type scale means everything is scale, the details are the right size, in the right place, the item has the exact scale dimensions of the prototype (to the point in 2 rail that you have proto48, that uses the proper distance between the rails for 1/4" scale which standard O is not).
For others it means 'scale size', that it is very close if not spot on. So if you put a scale box car up against other scale equipment, it would look like it belonged there. I suspect a lot of the Williams Equipment is more scale size than 'true scale'.
For me, if you put a supposedly scale item up against something you are sure is scale and it doesn't seem to fit with it, then it is likely semi scale *shrug*..