I think so, FWIW. In a van that is moving and with a little bad luck, physics can injure you.
You’re exactly right. One doctor was consulted for a “Jefferson Fracture”. This type of fracture frequently occurs from falls. It can also occur from hyper extension, such as what might occur in an attempt to clear the airway and intubate. There is no way to rule out injury during medical treatment at this point. The unconsciousness and all the other symptoms Gray had (breathing difficulty, convulsions, cardiac arrest, coma) are consistent with heroin overdose.