I have modified your code to give the regular Node a gray background and to insert an Auto Panel with a gray background around the Placeholder with margin: 1. Here is the result:
Note how the tops of the two gray rectangles have the same Y coordinate? The top-left corner of the regular node is at (0,0) and the top-left corner of the group’s Placeholder is at (100,0).
If you really want to line up the tops of the nodes, you should bind Node.position instead of Node.location.