Its a bit of a stretch to imagine the scenario where the Controller is distracted long enough for a vehicle to cross a runway, clear the taxiways, park up and switch off his radios.
And we've established he's parked up having a brew so clearly the incident wont be involving the vehicle, so why is anyone up before the beak?
In all seriousness, What kind of distraction is going to happen that will prevent the controller keeping an eye on the vehicle for the twenty-thirty seconds it will take to cross the runway
If the ADI controller can't keep at least half an eye on the thing that is
Blocking his runway without completely losing track of it on the airfield, then by all means make a runway vacated report part of the crossing clearance.
However I would worry about either the ADI controller who could become distracted to that extent or the working environment that could present that level of distraction.
For the avoidance of doubt, if a vehicle is carrying out an inspection of the runway, then I will require a vacated call as part of the clearance, but I have always worked at units that mean a portion of the runway is obscured from the VCR.
If I am clearing a vehicle to cross my active runway, within sight of the VCR then I do not require a vacated call.
At units with Tower, ground and vehicle UHF all being handled by a single controller there is enough RT to deal with without adding unnecessary calls.
Edit
An RT message is by no means definitive, how often have we seen both Vehicles and aircraft call vacated, when they are barely off the runway centreline?