The justification I have always heard for the duo lane to be in bot lane was that having two players down there gives you more early drake control which was more important than rift herald control. However, the new map changes have made bot lane significantly less safe especially for the vulnerable ADCs who want to farm safely and scale. On top of that, the changes have made top lane much safer. Further the new top objective, the voidgrubs, gives a large incentive for teams to focus top in the first 14 minutes where the duo lane may be more beneficial. Is early drake control really worth the sacrifice of safety and voidgrub control?
Only if they undid the “top and bot towers have different stats” change also. Which was their ham-fisted way of stopping lane swaps at level 1.