Have to disagree. Your #2 WR should be able to run all the same routes as your #1 WR.
Most times, your #1 WR gets double covered, depending on how well the rest of the WR’s on the team are. If the rest of the WR’s are sub-par/mediocre, good luck trying to spread the ball around.
I don’t know about you, but I would love to have the caliber of top WR’s the Dolphins have with Waddle and Hill. If Allen had that type of caliber #2 WR, Allen could be leading the league in passing.