I do believe the Salesman could have said this, back then there were so many individual options that some confusion could result. I've heard many stories from people, and I knew people who ordered cars in the 60s and 70s where the car showed up without or with different options. In this case it's possible that a sales guy was confused after quoting prices for a B body. Sometimes a sales manager would quash some options because HE KNEW they weren't available on that particular model, but some orders snuck through. When the cars were delivered to the dealer missing options, wrong engine, etc, some people refused to take them. Today since everything is all in 'Packages', we don't see these issues.
Considering 1970 model year was unveiled about Sept 20/69 and my order was written up on Sept 25/69 it wouldn't surprise me at all that the salesman was still reading is option book. The car on the showroom floor was a fully loaded GT, don't remember if it was a TNT or 6-Pac, black on black, buckets, floor shift auto, etc. I was sitting in the sales office looking at that car while the order was being built. I really wanted that GT as a convertible, but the salesman was adamant, no could do. However, he suggested I could options up a Fury III convertible and build my own GT convertible. Small stuff like buckets, console, floor shift, power windows, disc brakes, HD suspension and trailer hitch were easy. Included was thed removal of my trailer hitch from my 68 convertible and it's installation on the new car.
My engine options bounced between the 440 (350hp) and the hemi. The 440 won simply because the hemi was a lot more dollars, $440 vs $865 and the hemi had essentially no warranty. I don't think Mopar really wanted to sell the hemi engine at all regardless of car line since the warranty statement included a whole page of small print exclusions. Basically, if anything broke, you must have been racing which invalidated the warranty. My wife and I decided we really didn't want the risk. As it turned out, at just under 20,000 miles the 440 started to burn oil faster than fuel and Mopar replaced the rings, a bunch of pistons and a couple of valves, all under warranty.
Anyhow, I remember the whole process very well because it was the first new car I ever bought and as it turned out was the only one I ever got to custom configure. Everything since has, as you say, been bundles with very few options to customize. However, the dealer parts department will happily sell you the darndest things to satisfy your every whim as long as you've deep pockets.
My order as written.