NHFL9

Looking at redeeming miles for a trip from JFK-SIN in Business Class. DL only has medium and high available on most dates; AF has plenty of availability. According to the award chart JFK-SIN should be 120k roundtrip in Business Class. However, delta.com is pricing out the award ticket at 220,000 miles on AF JFK-CDG-SIN. (Looks like it is considering it US-Europe + Europe-Asia instead of US-Asia). I am not trying to build in a stopover, just a straight shot there and back with a connection to the next available flight at CDG. Is there an unpublished routing requirement to go via the Pacific on US-Asia awards? JFK-CDG-SIN is only 233 miles longer than JFK-NRT-SIN, so I can't see why such a routing would be prohibited. Any insights on this would be greatly appreciated.