Weird take, imo.
Havertz's tackle on Longstaff, like Nketiah on Vicario, not resulting in a nasty injury is coincidence. Havertz runs at high speed and lunges in with a straight leg, the height he jumps with and the distance he slides after missing Longstaff should tell you everything about the forces involved and the potential for injury. Mental attempt. Longstaff gets lucky, Havertz is less than a flaccid penis' length from planting his studs on his ankle, and when he does miss it's pure coincidence that Havertz trailing foot doesn't hit Longstaff standing foot higher up or that he gets caught between the trailing leg and the foot Havertz jumps in with.
Serious foul play
A tackle or challenge that endangers the safety of an opponent or uses excessive force or brutality must be sanctioned as serious foul play.
Any player who lunges at an opponent in challenging for the ball from the front, from the side or from behind using one or both legs, with excessive force or endangers the safety of an opponent is guilty of serious foul play.
Don't think it's a weird take (and this isn't football tribalism, I don't think you'll find an Arsenal supporter in the world who wouldn't want Havertz to get a three game suspension just to get him out of the XI!).
It's just a question of how do you want to decide red card situations. On intent (including recklessness)? On first order results (i.e., was contact made)? On second order results (i.e., what damage did the contact do)? Some combination of all three?
In theory, I'm ok with intent/recklessness being the main factor, regardless of results of that intent. I'd be ok with the ref sending off Havertz, stating "I don't care that you missed, that was seriously dangerous and you only missed by the grace of God or your own incompetence". But there's lots of raised boots in a game, and intent is very subjective. Including degree of contact into the equation adds an objective component. I don't think I want to see a season where the refs start brandishing reds for (necessarily subjective) potentially dangerous but missed high boots at a higher rate than they do now.
Finally, because this is also the VAR thread, I'll use this incident as an example of how VAR should work. Let's say it was called red on the pitch. VAR says "why". On field ref says "not sure about the contact, but incredibly reckless with a high, straight leg, studs up. Dangerous, therefore off". VAR says "cool, reasonable on field decision" and we carry on. If instead, on field ref says "cleaned him out, studs up closer to the knee than the ankle, straight leg", we now have a clear and obvious error in the facts to the ref's thought process. VAR tells ref where the contact actually was, sends him to the monitor to see two full-speed replays, and make another call. All over in 45 seconds (the delay for players pushing and arguing on the pitch is going to happen if there's VAR or not).