To be fair, 4-5-1 sometimes can be no different than 4-4-2, depending how the 4-5-1 is played...
If its a flat 5 man midfield, then fair enough. But if you have Cahill/Osman supporting the striker, then the only difference is a few yards on the pitch really, depending on the supporting midfielder/strikers tendency to get forward.
Its seems to be only really described as a "packed midfield" 4-5-1 when the likes of Everton play it. When Man Utd/Liverpool/Chelsea do, all of a sudden Sky jazz it up a bit as 4-1-3-2 or something.