[Jon can detect lies, like agents of the Desolation can generate extreme heat? Oh, that is interesting. It would be convenient if it worked on Bill, wouldn't it. Of course Ford isn't that lucky.]

Yes, he did. I suppose Bill told enough lies that he wanted a way to prove that what he was saying was the truth. Instead of everyone mistrusting anything he says on principle if a flood isn't involved.

[An afterthought:]

You can trust what he says while he's singing, but only if the rest of the barge is doing it, and he isn't doing the accompaniment himself.