I can say it's not even close to a foul because I talk with NFL officials and supervisors on a weekly basis. One of the major points of our discussions is the difference between the techincal and the practical. It is why the NFL allows wide receivers and split out backs to be on VIRTUALLY the same line, with the philosophy of a "single blade of grass" separating them. It's why players are routinely "offsides" on kickoffs and there is no flag. It's why putting 8 on the line and covering up an elegible number IS a foul, because the defense shouldn't have to guess who is a receiver and who isn't.
If everyone and their brother thinks he's a TE, then he's a TE.
If a bunch of internet officials and fans want to use still pictures and parse the letter of each rule and says it a foul, have at it. But I can tell you from meeting with these guys weekly, this isn't even close to something that's going to get called in the NFL.
NFL officials strongly believe you don't go looking for zebras in a herd of horses. If Denver thinks he's a TE, and Pittsburgh thinks he's a TE, then he's a TE, not a wump or any other trm you want to use for him. And if for some reason the L thinks it is a problem, then you tell him to move up next time, you don't drop a flag on it.