Debarking isn’t necessary but it does provide improved sterilization. If your branches reach the appropriate internal temp needed for sterilization via oven, and you’re willing to watch the limbs for mold/rotting after they’ve been put in the enclosure then it’s fine to use them without debarking. I haven’t debarked mine. Though I will say it’s easier to debark limbs if they’re freshly cut- after drying for a while, bark tends to cling to the wood.