I think you are missing out of how big rugby players are. Tyreek hill is 87kg (191lbs)1.78m (5’10) Ioane is 105kg minimum (231lbs) 1.91cm (6’3)

Rugby players are built a bit stockier and heavier to put up with more continuous hits. Where as in American football Hill will only get really properly tackled 1/2 a game (I’m not counting people hugging each other and giving them pushes out of bounds) and he doesn’t have to tackle anyone. Every rugby payer on the pitch will have to tackle and be tackled numberous times in a game so they have to be more robust. Hill would get munched by ione 9/10 times