This has been around for some time. It's a kind of musicians' modern folktale. Like most of these, though, it has a ring of truth and yes I've been asked to work for people very much like this too. Most of us could add bits.
My addition would be: "We want you to sing at the tables while the band (5-6 piece and amplified, with drum kit) plays on the stage". I didn't find this out until I got to the venue, mind you.
                                                    Joy