It is the tip for that branch. Even if there exist other commits building on the commit the current branch points to, the pointer is still at the tip for that branch.

The point is that a branch is simply a pointer to a commit that automatically encapsulates all of the parent commits.

I think I see what it means though. The branch uses that commit as a new tip to then branch off of, not necessarily meaning a new branch starts at the existing 'tip'.