No, not true. I have two accounts and two libraries - one for us oldies, and another for my grand children. There is a Classic for us, and they have a classic and a touch.
I suggest you set i Tunes to manually synch by clicking on edit, preferences, device, then check box "do not auto synch".
If you want two libraries, hold down shift when you launch i Tunes and choose potion to create new library. If you want two accounts , just create a new account. Remember to hold down shift if you wish to change to the alternate library. My grand children share a library but have different playlists and movie options.I tune will recognise each i Pod, as you register them when you first install them.