For Transorm.position 'Add Key' when selecting either x/y/z behaves inconsistently with 'Add Keyframe' btn on the toolbar

2) How can we reproduce it using the example you attached
1 Create new project or use attached
2 Create cube
3 Open animation window and create new animation clip
4 Press "Add Curve" and add Cube:Position
5 Select either x/y/z (for example x), Press "Add Keyframe"-button on the toolbar - notice that Keyframe is added with 1 dope (only X) (see image AddKeyframe.PNG)
6 Select either y/z (for example y) right click on it and select "Add Key" from context menu - notice that Keyframe is added with 3 dopes (X, Y ,Z)(see image AddKey.PNG)
Note:
For e.g. Cube: Box Collider.Center : 'Add Key' from context menu when selecting either x/y/z behaves same with 'Add Keyframe' btn on the toolbar