That's a good way to view Force Out as defined.IMO, it is written in that manner because runners are never forced TO a base, but are forced FROM a base when another runner/batter-runner gains the right to that base. Since the BR has yet to attain the right to a base, s/he cannot be forced to leave.
However, rules and discussions of them would be simpler (e.g. less wordy) if the definition included the BR. Is/was there a legitimate reason BR wasn't included?