[filmfact]

Exactly - mortars predictable trajectory against a background free of ground clutter make them easy to predict the future location of.

A drone optimally randomly dodging at treetop height is a much more difficult target.

[imtringued]

Why the hell would you dodge at tree top height? That makes absolutely no sense. Just fly a few centimeters off the ground without dodging and no air defense is going to hit you in a civilian area.