Sometimes sellers hide information to catch the unwary, sometimes sellers are simply uninformed and don't like to stand corrected. I remember an auction of a GZ250, a modern Suzuki with two exhausts pipes from the head -one per valve- but just one cylinder. The guy listed it as a "twin". I have the very same bike and sent him a message just in case he wanted to correct the description. I promise I was very polite but he replied angrily saying I was wrong and etc etc. I just searched in the Suzuki webpage and sent him a link to the oficial specs page. He finally modified the description but didn't admit he was wrong. Not that I expected it, but it was a clear case of "I'm stupid and damn proud of it".
The other day I emailed another seller to ask him in which shape were the theads on an oil pan he was selling. He replied that when checking them he noticed a crack in the pan and that he didn't think the pan was reusable, so he was withdrawing the auction and throwing it away. He indeed removed the auction, so I guess he also got rid of the pan.
If the subject is "If you don't know it for a fact, don't presume it to be true", I'm guilty. I talk about short chainguards, non-ribbed fenders and wrinkle tanks as peculiarities of the sandcast models. But I don't know that information for a fact. I got than information from popular knowledge and by reading in books, which I presume to be correct. Well, if popular information came from the same "authoritative" sources, and the author was wrong, then we have a false statement widely accepted as an universal truth. Like "my neighbour have a friend whose cousin was stolen a kidney and he woke up in a bath full of ice". We don't have the time to check every single statement we are told so we just give them the "benefit of doubt" unless proved wrong, specially if our money or wellbeing is not depending on them.
I recently bought a book autographed by Soichiro Honda himself. From what I asked the seller I got reasons to believe the autograph is genuine, but the seller didn't even got to meet Mr. Honda. So there was no witness of Mr. Honda signing the book. Some day I will give the book to my kids and will tell them from whom the autograph is. They trust their father so they won't ask how do I know: I say so and for them that's enough. If in 50 years time a calligrapher certifies that the signature doesn't belong to Mr. Honda, there will be nobody in the world to convince my kids that they have been wrong for such a long time. They assume it as a fact, in the same way that we assume that Benjamin Franklin flew a kite, that General Custer died heroically in Little Big Horn, that King Arthur's round table was actually round, or that it was Nero and nobody else who set Rome up in flames.