Son has started most of the games at LWF. I don't think that's his best role and I have some concerns about his fit to the system in that role. But I wouldn't say anyone half decent would just start out there. We also have Solomon, who at the very least is half decent. Neither is a "void"?
He's 18 without a ton of first team experience even in Belgium. Seemingly going somewhere where he's more likely to start most of the time. Seems like an understandable decision. I don't think that says anything negative about us.
Sons played 12 as cf and 8 as lwf this season according to transfermarkt.