Although if my recent experience is anything to go by then he wont get any bids when he auctions it and you will still get the GT for the starting price.
Not sure. I have bought from him before (long time ago) and he was a nice guy - he gave me a spare (VERY tired) Moulton mini to go with the one I'd bought for very little money and also chucked in a Bickerton in need of lots of love too.
Guess it's just one of those things and, as @winjohn pointed out, the GT will likely not make more money in an auction.
I’ve watched enough items from this seller to think it’s probably a genuine mistake. That said with the experience of sales they’ve had/volume of bikes they’ve sold you’d think they’d maybe have let that one go as it’s not going to make lots more in an auction While the size is unusual it’s not like it’s a misidentified Psyclone!