MAS 148 Long Range Launcher

Here's a little run down on how a Javelin works irl

Why is it when I use this weapon it wants to lock onto vacant unused vehicles & mounted weapons.
It doesn't really make an sense as they have no heat signature, they would have if they were recently used and still hot ! (I know mounted weapons are classed as vehicles since BF3)

I find this frustrating as my main is Engineer, being in a situation I will miss locking onto an enemy target because a mounted weapon is closer to me or the target or in line of sight of the vehicle I want to lock onto, I have to try to reposition quickly. It shouldn't happen locking onto a vacant mounted weapon or unused vehicle. I have to memorize where mounted weapons are on all maps so I know I am legit locking onto a LIVE ENEMY VEHICLE that may be parked behind a hill or something.

Locking onto a vehicle that was just abandoned, yeah it's fair to say that vehicle is still HOT, if you use a drone which has thermals and you see a soldier who goes prone and doesn't move you can see him go pale, which means he's cooling down & not as easy to spot, how the hell do we lock onto vehicles that are COLD ?

This weapon also is very weak against tanks and required multiple uses to even do significant damage to one.
Can this be changed ?