"I don"t understand why that gives an advantage over summiting your high bid at the onset"
A shill bidder will work up slowly to your max bid. They can tell when they get close because it doesn"t increase by the usual amount, just up to your max. If they go over you know they only bid just over your bid because they were inching up so you"re tempted to bid again. But either way they ran you up.
Wait to the last second if you want the item at a fair price (eBay shows you how much time is left). Or bid your max early and don"t bid again.