All I can say is that I have had 2 good experiences with them and both times I got the coral for less than I would have elsewhere. They are gorgeous pieces and I was very pleased with the experience.
If they are using "PROXY BIDDING" then you wont see the "other" bidder because the computer is working the bid system automatically. This is exactly what you'll see on other auctions as well. Nothing unusual about that.
FWIW I had the same reaction one time a while back when I was "Watching" an item on eBay. I was SURE the original seller was pushing the bids up by bidding with an alternate user ID or something like that. Then after watching several (and winning some of them via Proxy-Bidding) I realized what I was seeing.. or more importantly what I was NOT seeing LOL!!
Yeah, if you look at the times, the winning bid was put up before those other bids. 12am vs 3am. That guy was just trying to figure out what the winning bid was. It would have fooled me too, cause I thought you could see what the winning bid was.