The NRL made a statement early '25 that one of the things they look at in acts of foul play is whether there's mitigating factors. If there are, the punishment is less. The NRL's own guidelines say it's not a send off.
Quite frankly the video you posted doesn't support your claim of full force with the shoulder to the head. It shows head on head first, which is why Ponga's ear was bleeding, and then shoulder on shoulder and if there is any contact with the shoulder to the head, it's not full force. It's shoulder onto head. That itself is an important factor because if it's shoulder onto head, that doesn't meet the criteria for a send off.
It also shows Koula's height level dropping, which is another very important factor.
The fact that Ponga is only receiving a fine is pretty telling, as well. That same tackle at club level hasn't even been a send off.
At worst, it's a sin bin. It's just not a send off.