I agree with you re: never trust the salesman--but with some exceptions. In my case, the sales guy is a friend of mine and has no problem telling me he doesn't know or doesn't have the info. I don't bug him for constant updates, but he sends them occasionally including screen shots of his computer showing status, etc.
For those interested in my experience wrt timing, the truck is now listed as "bayed: ready (4B)" ETA to dealer is "pending dispatch." Since I'm in California, I'm hoping it'll catch a ride soon as there has to be a lot of vehicles shipped to my area.
FWIW, on GMC chat, I went from "order accepted" to "ready to ship" overnight with no status updates in between.