I can see exactly where you're coming from. Thorpe have made this decision and clearly not thought about the impact it will have on the queues (when will they learn, they'll never change, forever rushing into decisions and forgetting some important factors). As if waiting times are not long enough already!
Personally,I wonder why change the back rows at all? Yeah, The Swarm is the greatest ride Merlin have installed in years, it's been a success, and the ride experience is brilliant, facing forwards left or right side. And going backwards could be interesting too. I'll try it once, and even if I like it and the queueing system does work fine, I'll probably stick to normal seats.