That's not an eBay policy page, it just a guide offering some sensible advice.

Nobody can determine whether a price is 'too good to be true', it's not possible to differentiate between a seller using an unrealistically low price as 'bait' and another who doesn't know the value of their item so heavily underprices it. 

Nobody should be scammed over a vehicle -  consumer sites and programmes have been advising for as long as I recall that you don't pay money to a stranger. You go and collect your vehicle, inspect it, check the paperwork and then pay.