I'd say it was an honest mistake.

Compared to other dealers, a small one at that. Not like the "ramps have been polished" on an 1970's Bally 

I have purchased machines from Tony/Pinball Shed several times. Top bloke. He was always very pleasant to my wife and kids and looked after us with various machine purchases. I always found him to be completely honest.
The photo on the ebay listing clearly shows that the machine is a Gottlieb and not a Williams. Perhaps some inexperienced people on ebay who dont have any pins might not know the difference between the different models but the photos clear it up no probs.

The only gripe i ever had was that too many pinball collectors/restorers up here in QLD have their names down for anything in the "next container" which drove their prices up compared to Melbourne. I do note, that the Flinstones he has listed looks real good. 

Should drive the price DOWN, not UP. Straight out of a container should be cheaper, unless you Queenslanders work on a different economy