apply avatar mask to animation, doesn't the keyframe conversion of Obj that I directly added apply?

Unity Engine
,
1

I’m trying to use a weapon-equip animation for the Humanoid character,
Weapon locations vary from frame to frame, so something needs to be modified.

So I used the Animation tool to put GameObj, which I added directly to each hand of the character, and I modified the value of the position and rotation.

modify it like this and run it on the base layer, it plays as I modified it.
The problem was when I used Avatar mask because I only wanted to play the upper body.

But create another layer and apply the avatar mask, the modified GameObj Trasform(weapon_r) as shown in the picture is not applied and runs.

If I apply avatar mask to animation, doesn’t the keyframe conversion of GameObj that I directly added apply?