You touched on one massive reason why trials shouldn’t be taken too seriously, interchanges and reserve numbers. It depends on the game but usually there are heaps of reserves that get chopped and changed, because coaches can for trials.
This is why I don’t get how some people act like it’s a normal game lol. When interchanges are limited and you only have 17 players, it’s completely different. One of our strengths is resilience and fitness, which is irrelevant in those conditions, because the opposition can just make as many interchanges as they want.