Anyone seeing lower fuel economy in winter is probably due to other factors. These can be more idle time, thicker fluids, and possibly less complete evaporation while the engine is still cold.
My 2018 F150 2.7L EB is very sensitive to winter fuel. The instant winter fuel is put into the tank, MPG drops markedly. The engine is already warm, the truck is not cold starting and nothing else has changed. But MPG goes from 21 to 17 on my normal highway legs as soon as winter fuel goes in.