it would make sense for the vehicle crews to try and spot them so they at least know which direction to dive for cover…

I’d guess that Shahed-136s probably aren’t targeting vehicles. IIRC, they don’t – or at least didn’t – even have the ability to retarget in flight. The little short-range FPV drones, sure.

Shahed-136 is notable for being very long range, and I’d guess that they’d tend to go after fixed targets deep inside Ukraine.