Then it must be bugged because (in 3 and 4) I can make a new Control scene, add a ColorRect child save and get this:
[gd_scene format=2]
[node name="Control" type="Control"]
anchor_right = 1.0
anchor_bottom = 1.0
__meta__ = {
"_edit_use_anchors_": false
}
[node name="ColorRect" type="ColorRect" parent="."]
margin_right = 40.0
margin_bottom = 40.0
without the anchor button being touched or changing or indicating the change it made by turning off the anchor for that item when selected.
Or maybe i misunderstand.