According to Bulk Data 2.0, the DELETE request (2.5.4):
"Following the delete request, when subsequent requests are made to the polling location, the server SHALL return a 404 Not Found error and an associated FHIR OperationOutcome in JSON format."
During our testing, we found that SmartHealthIT reference server returns 400 for the sequence, and it returns 404 when the subsequenet request is another DELETE request.
See the discussion on zulip https://chat.fhir.org/#narrow/stream/179250-bulk-data/topic/Bulk.20Data.20delete.20request
According to Bulk Data 2.0, the DELETE request (2.5.4):
"Following the delete request, when subsequent requests are made to the polling location, the server SHALL return a 404 Not Found error and an associated FHIR OperationOutcome in JSON format."
That means such sequence shall be supported:
Export Request - Response 202 Delete Request - Resposne 202 Status Polling Request - Response 404
During our testing, we found that SmartHealthIT reference server returns 400 for the sequence, and it returns 404 when the subsequenet request is another DELETE request.