Commander stuns from a great hight

[AugustRush]

Is this meant to be or is it a bug,where a commander stuns you from a great hight.
The commander moved before i thought about Screen shot,but his location is marked with x.

 

[X4-JET]

It's like that for all mantis even I've killed mantis from down below. Pyros use thermo snipers can shot you from that distance aswell.