Cathay's website shows a 35-hour flight time for LAX-SYD, mostly due to a 12-hour layover in HKG (this compared to under 15-hours for the non-stops, and 18-hours for the 1-stoppers). Probably makes sense to use the free stopover on the outbound.

Return from SYD (through HKG) is timed well with the connection, so travel time shows as about 24 hours.

I suppose a 6-hour flight difference is OK when 1) you're on Cathay over Qantas or United, and 2) you can (apparently) actually get biz seats on CX.