Why are tiny scout drones the hottest thing on IRST?

So, because gaijin has made 10/10.3 UK ground absolute suffering I pretty much play SPAA and honestly I’ve kinda become cracked with the stormer HVM.
However what I’ve noticed is that for some reason tiny scout drones are the easiest things for IRST to pick up, it can be 20,000 feet away and in third person if I target it will always acquire a drone - easily. They are easy to be locked at any distance. Meanwhile the hot afterburning phantom it struggles to lock.
Not to mention that you cannot actually kill the tiny recon drones with the stormer as their hitbox wont allow you to.