Did new tests on the same smartphone with ARDK 2.3 (didn’t test with 2.1 or 2.2) and I see that things now stay in place as expected. I guess Niantic fixed something but I’m not sure what.
So, I suppose this huge hurdle (at least for me) has been fixed in ARDK 2.3, so I mention it here for others to know (and maybe prove me right or wrong).