What's up with field of view of wheeled vehicles?

[Meme779 4]

I noticed that all wheeled vehicles, including NATO tank destroyer, have a insane detection cone.

 

It is impossible to sneak up behind them to plant an explosive

 

You are automatically detected if you entered certain radius of a vehicle.

 

Going prone would help, but not guaranteed as you can still be detected if you are anywhere but behind a vehicle.

 

This would never happen with tracked vehicles, including the Nyx mini tank.

 

You can bang you head all day on a Nyx's hull and it still wouldn't give a ****.

 

Is this a bug or something?