No, nothing posted on this site is from Yanmar. The only "official" info we have is from Ebay. Ebay has none, zilch, zero, nada say as to what you do with your tractor outside of Ebay. Ebay has the right and the power to prevent you from selling anything they randomly choose because it's their business. I am sure that's even in the little writing that everybody doesn't read but clicks "I accept" when they sign up.
They may be regurgitating whatever the Yanmar reps sent them, but they CAN NOT stop you from selling a red or green or whatever color they choose to paint their equipment tractor that has 4 tires, a IC engine, 3 pnt hitch, a PTO, and sheet metal square corners outside of Ebay unless you are in fact copying their tractor and selling it w/out license. The limits in that message concerning used tractors are so over-stated that it is obviously not enforcable outside of eBay and even then they would have to check every single listing selling a tractor.
Does the whole mess make sense? Depends on how you look at it. Carroll Shelby won a similar case against Ford and all the kit car makers. Reproduction sheetmetal either is licensed or makes no reference directly to the OEM, brand, product, or model name/logos. Do unlicensed knock-offs get around the laws? Often for a time, but it usually catches up with them. Yanmar may be shooting themselves in the foot over this, but there's definitely no law against that.