Exactly. But we have the example in 2011 of Urban Meyer. He was out of coaching and working for ESPN. A report surfaced Nov. 17, 2011 that he had agreed to become the head coach at Ohio State. He denied it. So did the university. Then 11 days later on Nov. 28, 2011, after the season ended it was formally announced the Urban Meyer was the new head coach at Ohio State.
The schools don't want to take attention from the kids that are still playing. They don't want speculation as who the assistants will be. Cause even if Gruden is out of football, most of the assistants he's gonna hire are still coaching on teams that are playing. How would it look if assistant coaches on other teams are being asked before the season ends if they're gonna be joining Gruden's staff at Tennessee? Tee Martin (offensive coordinator at USC) is apparently already getting hit with these questions right now because his name has been rumored as a possible assistant in a Gruden staff at Tennessee and that's with nothing being formally announced.
If Tennessee named Gruden as the head coach today there would be absolute mayhem. Better to let the season end and make the official announcement like Ohio State did in 2011 with Urban Meyer.