In most cases, those items would have worn out many years ago, and would have been thrown by a PO. If I was buying any SOHC4 other than a CB750K0, I think I'd rather have a bike with newer, better replacement items than a rusted out, leaking (but original) exhaust, worn out (but original) shocks, cracked (but original) tires, split (but original) seat, chipped, faded and dented (but original) paint, etc etc.
That's why we have qualifiers like the word "mostly", as in "mostly original". I don't think anyone has claimed that there's anything wrong with replacing worn or damaged parts.
To claim that a motorcycle is "original" when you don't actually know if it is, is not being deceptive about the motorcycle, it's being deceptive about your level of knowledge about that motorcycle.
How deep do we want to dive? I've replaced parts on my CB750, and while they are "Genuine Honda" parts, they are new production. So if one really wants to get technical, my bike is not "factory original", despite being 100% Honda-made parts.
-The mufflers are HM 300's, but they have the paragraph stamped on the backsides RE it being against the law to use them on a bike newer than 1982.
-The clamp bands on the carb boots are connected to the same part # as in the 1973 CB750 Parts breakdown, but they are black with hex-head phillips screws. (Originals were silver-colored.)
I could go on, but the point I'm making is what really is "factory original"? We all seem to have different definitions of this. When Vic world builds sandcast biikes, he only uses parts manufactured by Honda in the late 60's- he's that picky. Whereas, some of us are just happy to have a complete functioning motorcycle that runs well and gets us where we want to go reliably.
Personally, What I'm looking for in a bike for sale depends on what I want to do with it. If I plan to take it to bike shows with the intent on winning "Best original", I'm looking for a bike with everything there- correct paint, yellow paint marks on the bolt heads.. you name it. If I want a cafe bike, I'll get a rolling frame since most of the body work will be replaced anyway. No matter what you're doing, as others have already said, you have to know about what you're buying. Sadly, eBay in general seems to breed suspicion that the sole purpose of sellers is to screw the buyers (with eBay gladly taking a cut of the profits).
I'll stop rambling now...