This just shows the mess having a mixture of model and unit driven rules can result in....

So you could have.

........l<---------------------------------19"----------------------->l
Target............................................ ...........................Rhino.Razorback

The razorback wishes to shoot the target, and rolls a spotting distance of 19".
The front of the tank, is within 19", but has no LOS.
The turret is not within 19", but does have LOS.

So the gunner can shoot the target, measuring the range from their gun, despite the fact that the range from gun to target is further than the night fight spotting distance, as you measure that range from somewhere else. The searchlight on the tank can illuminate the target without being able to draw LOS.

What a total mess,