I don't know whether this is the right place to mention this, but the documentation for this endpoint is incomplete.
https://developers.freshdesk.com/api/#satisfaction_rating_attributes
The endpoint (as far as I can see) only returns the survey results from the previous month unless you specify the created_since date.
If the dev team does get to read this: this isn't the first time I've run into this behaviour of requests requiring arguments to return all values (instead of requiring them to filter results). I understand that deleted/archived items wouldn't be shown by default but there appears to be some "magic date ranges" that are applied to some result sets.
I've use Pipedrive's API on a regular basis and it's 5X clearer than Freshdesk's. :-/