Was that a Polaris seat on a flight to Tel Aviv or indeed any Polaris flight? If not then not sure that has relevance to current incident.

There is a big difference between two folks walking several rows up to take seats near the front of a plane to Israel and same happening on a 1.5 h domestic flight, and an even bigger difference between a scenario that the FA ignores and one that they don't. Indeed when I have seen the latter it is almost always happening with tacit approval of flight crew (sometimes they may be airline staff even). There is also a big differentiation between when the FA doesn't 'care', as opposed to when they do 'care'. The key in this case is that the FAs did care and asked the passengers to go to their assigned seat. As far as can tell the plane didn't turn back because of the self upgrades but rather because passengers were riotously refusing to comply with a reasonable instruction from the flight crew.