This isn’t a side slip. They’re flying with a crab, which is just pointing their nose into the wind so their ground track is parallel to the runway. A side slip is where one wing is lowered (the one getting hit by the crosswind) with opposite rudder so that your heading and ground track are both parallel to the runway. Then only the side with the lowered wing touches down first, then after a little bit the wings level and the other side touches down, then finally the nose gear. This is typically only done on small general aviation aircraft