you’ll need to know up front that you want your commit applied into multiple places, so that you can place it on its own branch
More specifically, you'll need to know up front all the places you want your patch commit applied into so that you can determine where to start the patch branch from.
if you can anticipate where a commit may/will be need to applied
This is an important assumption.
The way I understand it, cherry picking is intended to be used in case of unanticipated migration of code.
its own branch
The patch branch should start at a common ancestor of all the target branches. Since the broken code is in all the target branches, it must be in at least one of their common ancestors.
If we don't start from a common ancestor and merge the patch into all the target branches, at least one of the target branches will get some extra change along with the patch.