Additive layer blend type has no effect when running a blend tree,Additive blend type layer has no effect

Hello, I have an animation blend tree running 3 aim poses on an additive layer and I don't see any effect at all. If I set my layer blend type to override then I see the result. I really want to have my aim poses to be additive since they run on top of my fullbody navigation and I don't want to loose details because of the override blend type of my layer. I'm I missing something? is it because additive doesn't work with blend tree?

thank you for your help :)