Toddler cast / splint question

My son (almost 3 years old) fractured his wrist and had a fiberglass cast/splint put on tonight. I put him to bed and I was watching him on the monitor to make sure he could get comfy and fall asleep. Next thing I knew, he had unwrapped the fabric around the outside of the cast (just at the top by his hand). I tried to wrap it back around the best I could but I definitely didn’t get it wrapped just like the doctor did.

My question is— is the outside wrap around the cast/splint important for the functionality? I’m hoping someone who has been through this with their kiddo or someone in the medical field might know the answer!