We enable Optical Image Stabilization (OIS) on devices that support it. However, iOS also offers "Automatic Image Stabilization" (AIS) in which the iPhone takes a series of images and merges them together for a sharper image.
Unfortunately, iOS does support AIS while shooting RAW. According to Apple, "By definition, RAW photos are unprocessed, and image stabilization involves processing the captured image."
If you'd like AIS the only way to perform this is by disabling RAW.