I'm posting this as an interesting comparison between a lifesize prop/set prop, and a model of the AT-ST... This is why there's "fudge room" in the world of props/models from films.
Notice how the cockpit of the model is elongated compared to the lifesize prop with Chewbacca popping out the top?
See how the forward thicker armor plate of the lifesize prop is more truncated than the model? Same movie, but that little detail gives two distinct impressions of the "length" of the cockpit from chinguns to top hatches.
There's other little subtle differences, and with other props and their models too (landspeeder, AT-TE, Jedi Starfighters, Airspeeders/Snowspeeders, etc.).
There's subtle differences between the models and the props that set them apart, and fudge up the supposed "scale" numbers.
Looking again at the toy:
It has the more truncated look of the lifesize prop than the film model.
Also on the cockpit arrangement. The cockpit is also design to hold figures that "don't give". This is a similar problem that 1:18 military toys have run into, making scale tanks/figures. The figures often have a difficult time fitting into their respective cockpit or hatch due to the fact that action figures are solid and don't give, whereas a real person's body/clothing shift and conform to fit into smaller openings, small seats, etc.
Hasbro's design of the cockpit is I'm sure partially due to the design of the toy (removable guns, removable "head", etc.), studiness, etc. But I'm also sure there's the issue of fitting two figures inside what by all diagrams, and the films themselves, shows to be a pretty cramped cockpit. They seem to have done away with the space in the back (where the Ewoks should go), to give extra room for the pilots to rest with their legs straight out and fit easier into the cockpit (probably thinking about Chewbacca too, a fairly large figure).
I'm still leaning towards this being to-scale, especially with the gap between models and lifesize props. This looks to me fairly spot on. The designer says an inch or so, but I'm holding to that being its height at ease. I think sitting up on its "haunches"(sp?) it's pretty darn accurate in height. I'm anxious to see one opened, in person, to compare with figures, measurements, etc. Finding SW scale on vehicles can be a real problem to solve at times. The AT-ST is sort of like the ROTS Jedi Fighters, in that it seems to change at times too, adding to the confusion. Right now though, I'm pretty excited for this piece.