Tega originally planned on signing after Wednesday's first official day for signing scholarship papers in order to make other visits. However, Auburn apparently pushed hard for a commitment and signing on Wednesday, and Tega ultimately went that route. Why? If I had to guess, Auburn told him that they could not guarantee a spot would be open for him if he held out until past signing day.
Tega is very raw, but has tons of athletic potential. He will likely redshirt (especially given the loss of workout times from his leg injury), but will be ready to have an impact on the field during the 2016 season. He was receiving big time attention from a number of programs such as Clemson, Notre Dame, LSU, Texas, and Tennessee. In picking Auburn, he chose to stay closer to the home of his guardians in Elmore, AL.
And yes, this does mean Auburn will have a Duke, Prince, King, Queen, and President on the team.