Yeah, so basically, the LAAT/i and /c used to be different sizes, because the C obviously has to carry an AT-TE, but the infantry version always looked a lot smaller and was in the ballpark of like, an attack helicopter in length. There aren't a lot of good "canon" sources for the LAAT length now IIRC, but they are the same as the old LAAT/c length in Legends, so I dunno if that's a copy error or somebody decided we can't possibly have two variants of the same ship be different length or what. On paper though it looks way too big, yeah.
Actually, looking it up the reference guide where the 28 meters comes from is FULL of editing errors. There's all kinds of misspelled names and incorrect image captions and event descriptions cited. It also has already been retconned, it apparently says Hammerheads are +300 meters, when later sources (and on screen depictions in comparison to like CR90) is more like 150 meters.