Looking at the replay, the only time Wieters came close to tagging Ichiro was on the initial attempt when Ichiro went by him. When they both came back to the plate, Wieters was not on top of the side closest to the mound, which is where Ichiro tagged the plate.
BTW - isn't there a rule that a fielder cannot cover an entire base or the plate? doesn't some of it have to be available to the runner? you can block it, but you can't just have a player just use his girth to completely cover it.