Well I was going to re-install and check out new updates but I guess not anymore. I don't care how helpful it is, if there is no details on the exact specification of what data is shared and no way to disable it, I won't support the product.
Contains following information: launcher identifier user identitifer (XUID) client session id (changes on restart) world session id (changes per world load, to be reused for later events) game version operating system name and version Java runtime version if client or server is modded (same information as on crash logs) server type (single player, Realms or other) game mode