Anybody who has ever ridden a skateboard or roller skates on asphalt knows that every square cm of it is inconsistent. Considering we're talking about a tread depth of less than 1mm, you'll find plenty of inconsistencies larger than that in any road in the USA. However, you and Achoo are right that there are no measurements to back it up. Then again, Sheldon's article doesn't have any either. My take: I honestly can't tell any difference between the various tires I have run over the years, many of them the same tires that pros and elites race on, so it must not be important.