SIN is a strange airport, I think the SATS does not want to make the F and J area too low class so they kick out all Y Class pax there (even if they have status!

A few years back when I was only MPO Silver (= OW RUBY) I was travelling on BA back to SYD in T Class. I went straight to the SATS premium checkin counter and the agent there said please goto the Y Class counter. I shower here my Oneworld status, she said, sorry this is for J and F Pax only!

It seems they ignore Oneworld rules there.