interactive rebase results across shared histories

Hello,

I've recently learnt how to consolidate and clean up the master branch's commit history. I've squashed/fixuped many commits thinking these would propagate to the children branches with whom it shares the earlier parts of the its history. However, this is not the case; switching to the child branch still shows the non-rebased (dirty) commit history from master. Am I misunderstanding something with this?

Thanks,