Robben and Sanchez can leave defenders behind with their pace alone, Robben blitzed Sergio Ramos for pace who is one of the quickest and most athletic CB's in football at the world cup despite starting 3 yards behind him. There's literally countless examples of him tearing teams apart with pace. And as I said in that post (which you convieniently ignore) the difference is negligible and all that matter's is the ability to go past players and make the runs in behind. Players who can do both have pace, players like Griezmann who do neither don't.
I am keeping it simple, your inability to comprehend basic football knowledge is your problem. Muller and David Silva have both played in the 10 position but both perform in completely separate ways, one is a playmaker the other is a specialist in the final 3rd. They have completely different skillsets despite being used in the same area. You only need to look at Griezmann's touch/heat maps to see the areas he spends most time in, or Athletico's shape without the ball. Again calling him a 2nd striker is just a reflection of his abilities, he doesn't get involved in much of the creative aspect because he's not particularly good at it.
This United side needs speed and creativity, Griezmann offers neither. He may be a better footballer than some of the names we're regularly linked with and would have a lot of value to a side which already has pace/quality forward but he lacks the assets we badly miss.