The central repository is the only point that knows (with 100% certainty) which ref the branch was set to before the force push.
Each distributed node only knows the ref the branch was pointing at the last time they fetched, so their certainty on what the branch looked like before the force push is much lower.
Each distributed node only knows the ref the branch was pointing at the last time they fetched, so their certainty on what the branch looked like before the force push is much lower.