True, they should make sure the runway is clear but they have four or more runways going at a time and if these guys were on a less used runway the focus could be on other more active runways. He was also confused about the "bs" call. Not many runway vacated calls in the US. Lots of problems, with plenty of blame to go around. Just frustrating to see fellow pilots constanty think they are somehow superior. One thing we all have in commen is we are human and make mistakes despite our training, nationality, or experience. Plenty of non standard rt in all countries including Europe.
631 clearly states contact the agency and state the emergency, it also states the advantages of using pan or mayday, not that they must be used. Should they have used it yes, would it have helped maybe, maybe not. It's hard to say without knowing what the controller was thinking.