He read at the Golden Bear several times. I don't think they needed to trick anyone into showing up by 1975, which is probably the year this ad was published.
I don't see how that's an inaccurate description, really. By the time he had established his reading schtick, it was part comedy. He may have hated the chaos and heckling, but he did not discourage it. He knew it was part of the draw for his readings - that there was a chance that they would be out of control. And he certainly read poems that were meant to make people laugh.
I guess what I'm saying is his first few readings in the first couple years may have been solemn poetic affairs, but they quickly distinguished themselves as entertainment. A weird and unique form of entertainment, but still entertainment. Don't forget he opened for Steve Martin at the Troubadour. I don't think a club would put a "serious" poet on before a comedian, unless they were trying to get the audience to leave.
Or it could just be the booker a the club had a sense of humor and the ad is tongue in cheek.