As you can see on the video, inverted works as relative. Am I doing something wrong?
This is occurring because the destination of the transition region is Marker A, a destination marker, rather than a destination region or loop region. Replace Marker A with a destination region or loop region (and set the transition region to target that new region) and inverse offset mode will work as you expect.
Inverted offset mode causes the playback position to jump to a position inside the magnet region, loop region, or destination region that’s the transition’s target that’s the same distance from the end of that region (as measured in bars) as the playback position was from the start of the transition region or magnet region at the start of its jump. In this case, the target is not such a region. (There is a transition region at the destination, but it isn’t the target of the transition and so isn’t actually involved in that transition; it’s just an unrelated bystander that happens to be nearby.) Since the target of the transition isn’t isn’t a region with an end point from which to measure an inverse offset, Studio falls back on the relative offset behavior, which only requires the target marker or region to have a start position.