Pretty sure that seller is also on ebay with many of the same listings. I question the authenticity of some of the items (jagwire kits and cane creek headsets) but I believe you'll receive what you order.
Theres always older giant frames on ebay for dirt cheap, this guys frames very well may be real. The manufacturers distribution rules don't apply when they sell excess production to a liquidator. Those rules are for brick and mortar retailers.