Thanks for giving us another argument, thing is that we talk about more practical use of anti-cheats for character such as speed hack, flying, super jump, teleport ect.
Also we consider scenarios when those anti-cheats are usefull to not harm performance but also stop harming people, this mean that apart rule to “never trust client” there is another “trust client depending on scenario”
To visualize it more here we have example:
We created a clicker game where you collect coins, some cheater make speed hack soo they don't have to walk that long, you of course patches it, but then another harder to patch exploit comes in place, it lerps player to coin's position, you also patch it. In one update you add speed boost potions, you also update your anti-cheat to don't fire false positives. Sadly for you, cheaters found another way to make their game easier, they've learnt that every 1/4 of second you check if they teleport, soo they made exploit that teleports them in blink of an eye to position and back to don't fire anti-cheat, you upgrade your anti-cheat, then you see performance drop, you repeat this game again and again, now your game is unplayable, cheaters found way that you can't patch, this mean automation and super quick teleports, you can't patch them anymore
Sorry for long story, as you can see, to patch one stupid exploit in your clicker you had to destroy performance, and even then cheaters found way to be better, this mean no matter what you will do, the better the anti-cheat is, the more it eats performance.
Now the “rule” that isn’t particullary true, “never trust client”, this is false, you can trust your client for some things like anti-cheat, you only have to know if you can do that!
Why? you may ask, see most of cheaters are random kids who dowload some .exe file from suspisious websites and then run it, they have zero knowledge about coding or even how cheats are made, many thinks that some guy in basement makes them and have this funny mask.
So at the end, 90% of cheaters can’t code this mean they can’t delete your scripts, update your game every week with bug fixes and then you will destroy cheaters mentally, who wants to update one thing every week?
Conclusion: Client-Side anticheats are mostly safe due to fact that no every exploiter can code and that many game genres are simply not able to be harmed by character exploits, this mean no server-side anti-cheat game possible, use secure remotes and client-side anti-cheat and you would be fine