Our whole company has relied on this for the past few months in order to communicate with some of our clients, rather than invite them into our private Slack. It's been wonderful.
There's actually another use case where a vendor provides a bot and wants users of the bot to be easily able to file help requests. We wrote an app for that and outlined our thinking here: https://www.transposit.com/blog/2019.09.17-amazon-slack-shar...