If you embed one SVG inside of another, it looks like the viewBox DPI for the inner SVG sets the DPI for the outer/containing SVG.
Designer 1.8.6, MacOS High Sierra 10.13.6
embedded_same_dpi.svg. Note how the circles are in the 4 corners
embedded_different_dpi.svg Note how circles are scaled toward the top left.
The only difference in the two files is the viewBox of inner SVG, which should not change the location of SVG elements in the containing SVG.
embedded_svg.zip