It is the big mob/line up that confuses me. Aren’t we supposed to remain seated until our boarding group is called? They do not announce, "all groups form one big line please".

So I come from the lounge, wait to the side, they call my group and I walk to the line. How the hell do I know where to join it? Do I go to the very back, even though 90% of the people are in later boarding groups?

if I go to the front, when they call my group, am I cutting in front?

Unless they enforce the “stay seated” rule, it is always going to leave you feeling like people are cutting in.