Interior Elevations from older-version projects will be migrated to ensure that they contain the same elements as before.
That is: the content of the Interior Elevation depends on whether element bounding boxes fall within the range (as determined by IE Markers). This is how Interior Elevations worked in earlier versions.
(To ensure this “old” display, the relevant Legacy option at Options > Project Preferences > Legacy is on by default when you migrate an earlier-version project to ARCHICAD 20).
If you turn the Legacy checkbox off, any newly placed Interior Elevations will display elements according to the new logic: if you use the Limited horizontal range, elements are shown which fall within the limit. If you use Infinite horizontal range, the entire model space within the Marker’s range is displayed (as in the case of Section or Elevation views).