If you have tried playing in 1.17 at all you will have noticed a disturbing amount of player desync. Getting out and in of boats can take a long time and multiple attempts. Entering and leaving portals sometimes glitches out your client and teleports you back into the portal many times, as well as makes your client fall through the ground until the chunks load in. Items are continuously going missing in your inventory and ghost items happen all the time.
I have not been able to find the result of all these desync issues but they make playing 1.17 a pain in the ass and seriously unstable.
If you actually try playing the game in 1.17 for a decent amount of time you will notice these issues pretty frequently.

Tested in survival in multiple servers.