The tar 'snakes' provide a different level of friction than does the standard road surface. Also, they are at a different level than the surrounding blacktop. I could well imagine that you'd feel it through the bars as you ride over them, from one or both of those effects (losing/re-gaining some traction instantaneously, or the suspension making a sudden change reacting to the road surface--or some combination of both). The faster you go, the more pronounced the effect would probably be.
It could be the tire itself, or any of a number of other things, but from your description it sounds most likely it was the road surface making the front end 'twitch'.
Find another set of similar corners without the 'tar snakes' (if you can) and see if the problem persists--AFTER you rule out the other things that have been mentioned. Don't take any chances, just in case you do have a mechanical issue.
For what it's worth, at 3K miles, my stock front tire was still good to go, but the rear was getting pretty worn.