I don’t know much about reed knives, but I’ve seen a few of them and were sharpened by Tom Blodgett from jende Industries (who also make reed knives). I don’t see a reason why a reed knife couldn’t be sharpened on the WEPS. Tom’s knives are done freehand and a bit convex because of it, so the edge may be more durable when scraping. He also finishes his reed knives on 15k Shapton stones.
That’s all I know. hope Tom pops in to solve the mystery.