The video quality isn't that great but I would submit that in any basketball game ever played if there is a triple whistle on the same contact, it's probably a foul.

You said you were wondering why the triple whistle. Pretty simple, it's near the intersection of three primary coverage areas. If we had to pick only 1 primary this is Trail because the defender who fouls was the primary defender on the ballhandler who was in Trails area and when the defender gets beat the defender is on the side of the ball handler nearest the Trail. You could argue that this Slots play because it is going away from the Trail, but this play is waaaay too far for Lead to have a whistle. Lead has better things to look at.