Oftentimes, the primary reason to redshirt a freshman post player is to let them develop physically so that they won't get pushed around by the more mature players they face in the games. That is not an issue with Polla. Also, the young man can play. He is not a project. He is already a "load" around the basket.
As others have noted, Polla already plays a "solid" all-around game for a college center. In very limited minutes, he has shown that he already may be the best rebounder on the team. He appears to have good basketball instincts. Even if his minutes are limited this season, it makes sense to play him. With Polla active now, OU has three (3) centers that can contribute in different ways, but all can contribute in positive ways. This is an advantage to be exploited now as most teams can only dream of this much depth at the 5.
As others have noted:
1. The experience he gains this year will make him more battle-tested next season as a sophomore, when he will be needed as one of the top two 5s on the team.
2. If he does go pro in Europe in 3 or 4 years, it would be silly to throw away a redshirt now for a 5th year that will never come.