I've thought the same thing. I've only ever experienced Everest when the Yeti was in his disco mode, so not sure what he looked like when he worked. But the Cars animatronics in the dark ride portion of Radiator Springs Racers are a good point of reference. Those are big cars, and seem to be sized up from their real life sizing to look right in the big dark ride warehouse building. Doc Hudson especially is HUGE, and definitely bigger than a 1951 Hudson was in real life (and those were big bathtub cars to start with).
Here's an interesting one minute long YouTube video that is some sort of WDI test footage or something. It features about one third of the animatronics from Radiator Springs Racers, but is taken from a cameraman standing in the ride while the various animatronics are cycled just for this footage. Interesting to think how, or why, WDI did this originally!