Now that I've seen it, I'm happy with a red card. First I only saw the 2nd head contact, that's only a yellow in isolation. But the first one...there's definitely an 'impact' - the player walked straight into him, forehead first. That's not negligible force, it's a clear red card. You'd send off for less force if it was a slap to the face.
Usually the forehead-to-forehead thing is 2 players already chest-to-chest, then one leans foreward. Not this one - he walks straight into him and makes contact at walking pace.
https://www.foxsports.com.au/video/football/epl/red-card-or-soft!697089
If anybody is able to get past geoblocking and see that aussie clip. It shows more than the clip above.
and while I haven't seen the same stuff
@Ciley Myrus is referring to, I suspect the instruction didn't cover a case quite like this one. I agree that forehead-to-forehead isn't an automatic red card....but usually it's done with 2 standing players with no impact. This wasn't that.