No, Crony, they can and do set minimums, and sometimes keep an option to reject all bids. IOW, it isn't entirely a real auction at all.
Here, I just quickly googled this up:
Selling a Home Via Auction Growing in Popularity — The Real Estate Bloggers
Selling a Home Via Auction Growing in Popularity
October 27th, 2006 | Real Estate Sales
If you are looking at selling your home quickly, a growing trend in the country is using the auction system. Homes sold via auction increased by 5.9 percent in 2006 and auctions have been trending upwards over the past 5 years.
While using an auction may seem unconventional, people interested in a quick sale have used this effectively. There is an excitement that auctions bring that is done correctly can significantly increase the price of a sale, and
if you use the minimum bids correctly, you will be out only the fees to the auctioneer if the home does not sell.