When I see something like this I can't decide whether the seller has no knowledge of the item so doesn't know what a potential buyer needs to know, or the seller does not understand that a possible buyer does not know what they know.
The seller may know this is lens has a Canon mount, for example, but just hasn't thought to mention it.
I suspect in this case it is a lack of knowledge. To a non-photographer, it is just a lens.
Could have been worse. I've seen badly out of focus photos on Ebay and wondered, "Do you think this photo is going to help you sell that?"
Dave