Cancelo was sent off after about 10 minutes in the 3-2 home victory against City, for a 'last-man' foul when Welbeck was through. My view is that Haaland pushing Webster over was a more obvious foul than that one even though, on balance, Cancelo fouled Welbeck.
Agree with both your basic points relating to Webster and Sanchez. I also agree with all your subsequent posts, which amounts to:
-- it was a shove by Haaland on Webster, which constitutes a foul (to add, it's defying the laws of physics to expect Webster to stay on his feet in such a situation)...