For the test I used the Endpoints_Disconnected.csv & PrivilegedAccounts_Disconnected_endpointType.csv files which are found in ../CA/AccessControlServer/IAM_Suite/Access Control/tools/samples/feeder
Put them in the alphabetic order, i.e. Accounts first (which I expected would cause issues since as per above statement the Endpoints need to be defined first) Also the Accounts file's time stamp would be older than the Endpoints one - to verify if the files are processed FIFO. I also tried it in the reverse order with the file stamp, ie. Endpoints is older Accounts is newer.
Either way, importing both files at once correctly created the Endpoint and Account in ENTM. (If only the Accounts.csv was put alone as expected an error was issued that the Endpoint did not exist)
Also, as to see from the time stamps and the file name of the files in the 'processed' folder the Endpoints.csv was processed first the Accounts.csv.