Protocol driver expects that its ProtocolReceive handler is called at DISPATCH_LEVEL (refer the DDK documentation where it is explicitely specified “…ProtocolReceive runs at IRQL = DISPATCH_LEVEL…”).
Since protocol driver assumes that it was called at DISPATCH_LEVEL then it could use KeAcquireSpinLock/KeReleaseSpinLockFromDpcLevel, an example instead KeAcquireSpinLock/KeReleaseSpinLock or something similar. It is not a good sample but when called on DISPATCH_LEVEL both pairs work on the same way.