I watch some clips about it I thought it was just for fun but didn't know that it was really a competition, just come to think of it receiving a direct hit on the face if they get it like most of the time I'm sure there will be in long term there will be a great consequences with that. I really don't think this is some kind of sport at all.
the first time i watch the video in yt i know it was a pro sport and if its for fun they wont be in an organized place with referees and staffs that assist them after the match finish and you can see before ter or after a match the players are check to see if they are in good condition and i think there are creams that they put and massage on their face to lessen the impact of the slap . this is thier choice tho so they are ready if whatever happens to them