SQD Discrepancy Processing Time DP: Request submitted Oct 16, 2022 for UA-operated flights in Sept 2022. Got response in Feb 17, 2023 with SQD credited back. Having to submit the discrepancy form again for another UA operated flights this Feb... I guess I won't get a response until July 2023
I don't see AC has a specific form for SQM discrepancy. I only got 50% Miles as SQM with a Flex Economy ticket, operated by UA though. Looks like I will need to try the Customer Service Form.
It is quite possible AC booked you into a UA fare bucket earning only 50% SQM (STL, IIRC).