Why would you waste 2 maybe even 3-4 bench rotations on edge back rowers , wheee much like centres they can spend chunks of the game with the ball on the opposite side of the field not doing much .
It’s very rare for the ball , both in defence and attack to not engage the middle third in 2-3 plays . Which means they’re constantly working constantly moving , constantly closing down gaps , cobstantly running lines constantly actually taking hit ups , constantly tackling etc. And because everyone in the middle is soo massive , they also have to be massive To deal with the collision . And then you have the issue if you do play a middle more minutes day 80 mins a a game for 5 years , you’ve shortened the lifespan of a weapon middle like one Jason Taumalolo . Thats the cautionary tale with overplaying middles . People forget just how dominant he was up until the last 2 years . He should have had his minutes chopped to 60 a long time ago.
There’s are factors in why the middles take up the majority of the allowable replacements I believe it’s 8 now . So 2 off (maybe 3) at 20-30m , swapped back around at 60 mins (on average ) that’s now 4-6 of your 8 replacements gone . You now have max 4 , more likely 3 replacements you can make across 2 other bench players and the rest of your team .
chuck in injuries , unless they’re caused by foul play , they don’t count as a replacement , and if you get 2 Hias you can activate the 18th man , but that’s not until 15 mins after the player has been taken off so that’s not that handy either .
Generally speaking there’s probably 1 bench rotation you might have spare at the end of the game . Which is why we were chucking Mason in for a cameo .
The HIA rule has thrown the cat amongst the pigeons re. Bench rotation , and I honestly believe the more teams treat it with the respect of an F1 pit stop , and all the strategy that goes into that , the closer they are to having fresh troops at the end of the game .
That’s a really long answer to your question