Thank you !They sometimes do ask PCC if the stay is close to 6 months, say 5 months. Its purely upon discretion types.
Call and tell them about the request decline and ask what needs to be done next. You cannot argue based on the fact that you stayed only for 5 months and you are not required to get PCC.
I just called CIC, he told me to upload a LOE alongwith the Decline screenshot and upto officer's discretion. I can only hope the officer accepts it. There is no other option, since the Singapore website does not provide COC for less that 6 months stay.