Not to be that guy but there is still a difference between Malphite's Ult and Yasuo.
Malphite's ult is in fact a Dash, but he is Immune to CC effects. Similar to Vi, Sion.
Yasuo is not a dash, it is a blink. In game terms, he does not physically travel the distance between the two points, he simply appears at his target location.
It is a somewhat minor clarification since in both cases, Poppy W won't stop them. However since Vi and Malphite travel the actual distance, they can still be damaged or even killed by something they pass over. If Vi passes through a Jinx trap, she'll still get to her target, but if the trap's duration has any "left over" after her ult, she'll still be snared on arrival. Yasuo won't because he blinks to the target.