@omarel As noted, I am already familiar with the SVG spec, viewBox, viewport and the related coordinate systems and transform behaviors.
Your time and input is appreciated, however I am not looking to get into a discussion about SVG viewBox here. It is an unrelated and slightly complex topic if you have not spent time studying it.
The point is that introducing Draggable changes the position of the SVG element, adding some kind of invisible margin / boundary. Remove Draggable, and the SVG as well as its surrounding container go back to behaving the way they normally do.