He did interfere as the catch no doubt would have been made had he not been there. But the big play was when Alex Gonzalez made the error.
Great game anyway, unless you're a Cub fan.
He would have made the catch, but if the Cubs really want to blow the PR game, they should blame one fan for the collapse.
That ball could easily have been fouled another 10 rows into the stands, and the score would still be the same.