Karoline, I think the writers didn't want to limit the types of changelings purely by points (note my ganesha example). They are relying on the GMs to determine what types of changelings they want and how they manifest. If we built the metahumans and metavariants with surge rules compared to humans we would find they would require a lot more points (an elf would cost at least 50 points). This is where judgement comes into being a GM and learning where to say yes to a concept and where to say no.
If it has a mechanical advantage then count it towards a spread. If it has a minimal, overlapping, or negligible effect than I would not count it or reduce the cost. Also compare the cost to other sapients/metavariants to see if the costs are similar.