Same thing when I built mine a few years ago. I had never remembered encountering that before, even building a few other AMT truck kits back in the '70s-'80s.
I don't recall any huge problems figuring out the build sequence. More troubling were the huge slightly mis-matched seams to be removed from virtually every part.
It was a lot of 'drudge' work, but it built up pretty nicely in the end with some home-made Chicago Streets & Sanitation decals.
