I had something similar at JFK over 2x23 KF limit (which I could repack to comply) and short-checking my luggage to SIN instead of the connecting flight 12 hours after arrival. They refused. I didn't fight further and requested for offloading at Changi with no questions asked.

My impression is that they follow the books, very inflexible and the explanation is quite crude / rude. They are way way way off customer service standard that SQ brand calls for.