I don't think the availability of Charms thematic to your spirit shape in other shapes detracts from the focus on your spirit shape. Quite the opposite. Your spirit shape is part of your nature, always, and your Charms reflect that nature. Your spirit shape is one of the central pillars of your identity - maybe not the only factor that might inspire Charm choices, but presumably you chose that animal because you wanted to explore its themes, so it's going to influence a big chunk of your Charm choices. In this way, your spirit shape is reflected in your capabilities no matter what shape the situation...