rinat hits the old (deprecated) API and seems to no longer be actively supported. you’re probably better off using the current API (http://api.inaturalist.org/v1/docs/#!/Observations/get_observations) directly, which will give you all the details of the identifications associated with a given observation.
there’s also this, which i haven’t looked at in depth myself, but might offer an easier way to access the current API:
if you want to change the CSV export, you probably should make that known over here rather than in a separate request.: https://forum.inaturalist.org/t/data-users-what-are-your-use-cases-and-requests-for-exporting-data/2972.
i don’t fully understand your use case. do you actually need the data laid out in a table format, or are you just trying to see the ids on observations without having to go into each individual observation one by one?