Why does the EV berry not affect Starmie?

Question

If I give a qualot berry (lowers defence EV's) to my gardevoir with 252 spatk ev's and 252 speed ev's it says "It's base defence won't go lower". And when I give it to my starmie with the same EV's it says: " It won't have any effect" What is the difference?

Answer 1

Stat won´t go lower - happiness effect applies, ev-reducing not

Won´t have any effect - neither effect applies

Answer 2

The first one means that your Gardevoir can still raise its friendship, but the Defence is already lowered to the max. So you can use the berry still just to raise the friendship.

The second one means it has maxed Friendship and defence was lowered to the max, so the berry wont have effect on it anymore.