Medusa attacking nyx tower

A weird thing I have noticed is that whenever I am attacking an island where nyx tower is placed at front of the gate, medusas’ in my troop try to attack it. Only medusas’. They ignore the nyx when it’s on the defense path, like they should, but I don’t know what happens at the front of the gate. The first time i thought maybe there were some enemy they were attacking, but it happened again, and I am sure there were no enemy troops. Anyone else noticed this?

All units can attack nyx towers at the gate. It’s in the field of play. 

You could attack with your Hero the Nyx tower at the gate. So as @dumps said: it’s normal!

The lesson is: don’t put towers at the gate! It’s a waste. Or do, so I can steamroll your defenses.

Oh, okay, i didn’t know that, so i was kinda surprised.