Hello @Eli,
Welcome to the forum, your question is absolutely fine, no worry 
In Rasa X, when you clicked the button it displayed the payload because that the intented behavior. “/drink” meant that the intent drink is provoke and “{drink: Coffee}” mean the slot drink is assigned the value “Coffee”. That’s the exact flow of actions if an user said “coffee please”. But because the user didn’t type a message, but click on the button, therefore the payload got executed without needing to predict user’s message, and Rasa X print that payload out.
If you build a custom UI, then you can control how the user’s message is displayed when they click on the button. Rasa X is simply designed to do it that way (from what i know).