I would have had the same thought, but BR/CX/SQ operate flights with J/PE/Y on some routes that are 3-5 hours in length, like SIN-HKG/TPE.

The offering makes sense for me - lie-flat is nice on any flight, especially in the 4-5 hour+ range, but the price premium is high on these routes. So having PE as an option is appealing - will have to see what the pricing is over time.