Yeah, don't get that. Compared to the Matsuaku challenge, Pogba at least is in the same postcode as the ball, but clips Bellerin's heal after which he takes a further couple of steps and goes to ground - Clearly a penalty.
Not sure what Matsuaku is actually trying to do though, he just kicks Salah on the back of the foot, there's no way he can get to the ball without going through him so not sure how anyone can argue it wasn't a foul

Just because Salah puts the kicked foot down and then goes to ground does not negate the foul - it's kicking the player that is a foul not knocking them over. The fall is just really to make the ref make a decision, but it's really no different to Bellerin just that one was running and the other wasn't. If the officials will not give a penalty if the attacker stays on his feet then why should they not fall?