Well, I just checked the 1996 Essential Guide to Vehicles and Vessels and it has the 22 x 15 figure. I'd check the ROTS Incredible Cross-Sections but I don't have my copy with me.
The Juggernauts (and Turbo-tanks) were always intended to be roughly equivalent to the AT-AT ... I think confusion came from the attributed size(s) of the AT-AT: Older sources pegged it at 15 meters high, while newer sources, using supposedly more accurate measurements from the film, make it 22.5. So I guess when they "upped" the size of the AT-AT they had to up the Turbo-tank as well .... like I said, I'm not that up to speed on dimensions but I have no reason to distrust the published sources.
The Databank suggests there is also some difference in the guns and stuff, but I'm not technically-minded enough to look into it.