It is unfortunate perhaps that the seller didn't know the finer details of the machine, but should we really expect them to? Do I expect lay-people to know how to decode a Kenmore model number? No, many people out there can't tell a 2 year old washer from a 20 year old washer. Those people know a lot of things about stuff we don't, it's how the world works.
The machine's styling is very mid-20th century and though the Avocado color gives away its origin without looking at anything else, if that same machine were white, it would definitely be passable as a 1940s machine to the vast majority of people.
Giving the seller a hard time about their mistake is unwarranted.
Gordon