To really test this theory, you could simulate all 55 years, say, 1000 times. Randomly pick a team as winning the championship each year. Find out what percentage of the time at least one of those 55 championships broke the proposed rule. If that percentage exceeds, say, 95%, then this is a very strong rule.
I agree w/durvasa, kyrodis, sam cassell, and others; the categories here are so wide-ranging that of course you're going to get that result. I'm sure you could get the same result with a whole bunch of factors: 4-5-6 year veterans, Undrafted Free Agents, White Jerseys