It happens, unfortunately.
The local Habitat Restore does that to collectors all the time, too. It sucks. And, yes, we've seen this situation around here before. More experienced collectors will sometimes post an urgent request that nobody 'look' for the appliance they've found online, please.
The potential good news - most of the people who jack up prices on 'our' collectibles end up selling them later for much less. So, keep an eye out.
As to pre-rinsing, that's just one of those things where everybody is different. I refuse, flat out refuse and that's that. My brother and my father WASH and SCRUB the dishes before they go into the dishwasher and that was one of the tattle-tail fights my brother and I had throughout the 1960's and early 1970's...Panthera isn't scrubbing everything before it goes into the dishwasher!
I could not care less what other people do, but refuse, absolutely refuse to be one of those aging queens who thinks there are bonus points for unnecessary work.
KA dishwashers of that era do need a reasonable pre-scrape. Not hysterical, just reasonable. Potscrubbers, between their outstanding filters and soft-food 'grinders' (I know, darlings, I know) actually only needed bones and olive pits removed. They cleaned better than the KA and that's been something very, very disconcerting to many, even here. Here's why:
KA dishwashers are works of art. They're super well made, very pretty, run well and sound great when they're running. Sort of like a DeSoto or a Cadillac, back when they actually weren't gussied up Chevys.
GE Potscrubbers were made of 'plastic'. They used shaded pole motors (the horror of it all). They looked as if they'd been designed by the same committee who made the elephant and then the final design was handed over to a band of dyspeptic bean-counters. Who then turned them over to a bunch of hipies on bad acid trips who threw in faux wood and chrome-plated plastic. They sounded like someone left a few screws in the sump (which explained the mysterious rattles) and, worst of all, normal earners could afford them.
Rather like my grandfather who could have afforded a Cadillac limousine and driver for each day of the week but drove a Buick because nobody else in the neighbourhood drove one and he didn't want to offend the neighbours.