Description of problem:
When querying the API for a single observation in JS with “await inatjs.observations.fetch(observation.id)” the Object retrieved has a property Observation.taxon.defaultPhoto as well as Observation.taxon.default_photo, from what I can see it gives back the identical object.
It may be an overreach for inatjs to be creating JS models, but that’s what it does and why you’re seeing additional attributes not directly present in API responses.