Not sure if this has been discussed-WAS and NYC aren't permitted in award searches, is this by design because otherwise it would produce too many results?

Also, doing an award search for IAD-SEZ this morning. Delta.com has never let me do a rd trip search successfully for this routing (which includes an AF codeshare operated by Air Seychelles CDG-SEZ). It always makes me do multi-city, despite the fact the the outbound and inbound are completed with a <24hr layover in CDG. Comparatively, I can do IAD-MRU without a problem via rd trip search.