Comment by Kiuhrly1

What's interesting is that the Minecraft netcode is so bad that your client physics doesn't even need to be accurate or even correct for it to work. There is no verification that the client's inputs actually match the player's resulting position (not that they're even sent to the server). The client sends their position to the server, the server does some simple checks for flying, speed hacks, phasing through walls, and that's about it. Which is why there's all sorts of interesting movement cheats, and also why most servers run some kind of third-party anticheat plugin.