Maybe they want to keep Daniels at one position all season (guard) and they simply do not like Kush at center. In that case, once Daniels takes Kush’s starting LG job, there would be no viable back up center.
The Bears could possibly go with 9 offensive lineman, and the only way i think Grasu makes the team. There are 7 locks:
Leno - LT
Massie - RT
Long - RG
Kush - Swing guard
Daniels - LG
Whitehair - C
Coward - Swing Tackle
And then you choose 2 out of the remaining 3:
Sowell - Swing Tackle
Morgan - Swing Guard
Grasu - back up C
I could see Grasu potentially beat out one of those two.