It could also be as simple as they want both players to have time with the 1s in training camp. Even if Penning starts, it's unlikely he will take every single snap so Udoh will get some playing time at RT during the regular season. But, it's also an opportunity to see how Udoh plays with the 1s. I think it's unlikely they start Udoh over Penning because he doesn't have Panning's potential unless Udoh blows them away. But I'm just guessing.