I think the issue here is that for the assets you have put in the AimOffset, you seem to set the BasePoseAnimation in the Additve settings to itself, judging from the screenshots.
It should rather be the pose it should be additive to, so in this case the first frame of your idle animation I assume.
The reason is that Unreal basically finds the “difference” between the BasePose and the Additive Animation. When using the animation in an AimOffset or AnimationBlueprint, not the pose itself is used, but rather that previously mentioned difference.
If you set the additive basepose to the animation itself, there is no difference between the poses, so when applied in some way, you basically add 0 to all relevant values(transforms, etc.) and so it does nothing really.