Yeah this is disgusting and happening a lot now. Sometimes, very occasionally, they do legit have an actual minor knock to the head which yes, may have hurt a bit. Still, they should not be stopping the game to go over only for the player to be getting straight up again within seconds.Ironically, they lost the game at Anfield in the 6th or 7th minute of 'time wasting' time.
One of the recent tactics we see now is defending players going down in the box holding their head, knowing full well the ref will stop the game and in most cases the opposition attack, the ref will run over, check on him, he'll rub his head, get up and then play on from a drop ball that's took out all the sting and pressure from the attack. If it happens, then the ref should immediately call on the physio (because it's a head 'injury') before he gets to the player and subsequently, after 'treatment' the player will leave the pitch and wait to be called back on, let's see if being a man down for an attack cuts it out.
The head injury exploitation is a real problem because even if they added back on the time wasted, it's the impact of halting attacks and specific periods of play. If they adopted a rugby style approach where the ref can signal medical people onto the pitch during actual play this could lead to problems though with medical staff tactically running on deliberately to interfere with play. So I don't think there is an easy solution to this one other than to take the risk and ignore the head injuries on the basis that 99% of them are minor and the player is fine. Unfortunately in the world we live in now where health and safety is top priority, that will never happen. The underlying issue with the majority of these things is sportsmanship and the attitudes of players that want to win at any cost. I see more sportsmanship during local Sunday league matches that get rough. At least they honestly punch each other in the heads.