He has played this role last season in a lot of big games and played them well. He had a great game against Liverpool on the left, against AC Milan from the bench as well. Against city too iirc.
I agree. He is a #8/10 hybrid, like KdB/Grealish/Iniesta etc. He is wasted at CM and isnt really a natural #10 like Bruno either. He plays best as the attacking #8 in a 4-3-3 or as a false #8/wide playmaker in a 4-2-3-1. He is basically playing the role Mata usually plays for us from the right. Grealish plays similarly for Aston Villa. If you see Pogba's heatmap, he was basically playing as an attacking #8 from the left.
So in that sense he is not a left winger, but rather a playmaker from the left.