Unfortunately whenever ebay writes policies in good faith people will take advantage of the system - in this common scenario sellers who use retail arbitrage often list for example the complete parts list of a manufacturer whilst holding no stock or even an agreement to drop ship, then shop around to try and buy cheaper and fulfill an order often unsuccesfully in a reasonable timescale if at all.
They do not even know if the item is available and quite often invalidate any guarantee or warranty being an unauthorised reseller - these items are technically second hand in terms of selling in that the dealer sells to them then they sell it on without authority.
It is difficult to detect before purchasing but a seller with every conceivable part or item is a potential problem.
ebay are not the only online platform which attracts these practices - each platform deals with it in different degrees of sanction.
Do ebay turn a blind eye to this practice - possibly by putting the onus on the seller - a reluctance to lose revenue may play a part in the practice being against ebay policy but remaining without serious sanction.
