Most professional players really don't need to train physically every day. These days it's more mental focus and hunger/ intensity to win on game day.
Back in the heydays most players worked full time and only trained once a week then a half an hour warm up before the game. This is how the won 11 premierships in a row with very little training.
They don't need to train physically every day, but they have a routine with recovery sessions, rest days and training. All of the sports science seems to point to the importance of recovery sessions, and when you're dealing with elite athletes in contact sports they're pretty important to reduce the likelihood of injury or manage existing ones.
While the blokes in the past held down full time jobs, they weren't going out on the weekends and playing against blokes who were full time professional athletes, so it's a bit like comparing oranges and apples.
Anyway, it shouldn't be a massive deal if the club manages it properly, but the point is that the club does need to manage it. If the club took the mindset "it's only a 3 hour flight" and flogged the players to get through 5 days worth of sessions in 3 days, it'd border on negligence, and it wouldn't improve performance.