I see a lot of issues with bathroom breaks, not just SBux but other places as well, and a lot of “just tell them you legally get to use the bathroom” without any citations. Below is a link to an OSHA article outlining clearly where it's stated.
When I was a SM and GM before that running a store within the confines of the law was paramount and knowing where to find that info was important. As I see more and more sketchy managers coming in it's important for partners to have the ability to pull the regulations and forced managers to operate within the confines of the law.
https://www.oshaeducationcenter.com/articles/restroom-breaks/
Im here by offering that anyone who has a question and regulations, feel free to send me a message and I will do my best to respond with a link to the specific regulations that cover that area. And if you need with phrasing a response to a manager I will help you there too since I know some people are not confrontational in their approach to life, which is okay btw.