It would only be about adding a pointer — if data were mutable. But this is the Erlang VM and data is immutable. If you want someone who holds an older reference to data not to see it change, your only option is to rewrite the whole linked list.
Note that this isn’t the case with prepending since a new list head can point to any existing tail without that tail having to change. That’s why the common recursive pattern is to prepend a new head for each element during an iteration and to then reverse once (rewrite once); one rewrite for the whole list rather than one list rewrite per element added.
