I think that is true but Fuller did not have elite speed when he showed up at ND. He had a 4.53 40 as a senior in HS and that was a big jump from his prior year. He was sub 4.4 at the combine. Not sure how he gained that much extra speed.
From the articles and posts that I have seen on Keys I bet he has better than 4.53 speed. If he runs great routes, then I think he might be best compared to KS speed who could go over the top of a defense. How are his hands?
Keys and Lenzy will give Long two players that can stress a defense with speed. We just need to make sure we have a QB that can take advantage of it by executing the playbook.