Analytics API 404 mapping Zendesk CSAT to Genesys Cloud

Just noticed that the Analytics API returns a 404 when trying to fetch CSAT data mapped from Zendesk tickets to Genesys Cloud interactions.

“Custom attributes are not supported in the base query for digital channels.”

The analytics query endpoints seem to ignore the custom attribute filter entirely. Is this a known limitation for Zendesk-to-GC migrations?