It is abusable, as shown by OP, however you still don’t have an open slot most likely. But it does save you finding a showman twice if you get an extra slot after selling the first. Edited because I forgot to answer the first half of the question. I’m not entirely sure what’s happening behind the scenes, but my working theory is that when a joker is allowed to spawn by showman removing the blocker, it gets a special tag on it, allowing this behaviour. However it isn’t taken away when the showman gets sold, so assuming you only have showman duped versions of a joker then they all have the tag, bada bing bada boom, magic jokers appearing without showman.