Well, this is quite a surprising turn of events!
I still have not received the status credit adjustment from SQ. However, 2 days after sending the email saying I would raise my case with ACA instead (which I haven't actually done yet) I received a call from a supervisor. I missed the original call but she has just called back. They have today upgraded my account to Gold on the basis that I would've had 500SC+ had the status credits posted at the original earn rate! As this was the whole reason I booked the SQ fare class I'm ecstatic with this outcome! Will just wait and see if SQ if ever come to the party, if they do the additional points will just be the icing on the cake.
I can't say for sure that mentioning the ACA has influenced this outcome, I was certainly getting nowhere until then!