I’m trying to use a button group (with no gaps) to display bunch of buttons when only one is selected (like is radio buttons, but looking like regular buttons. My usecase is display a switcher for Month/Week/Day/Agenda view in a calendar. I think joined buttons is the best UI for this and I was using the old react-based Polaris in similar scenarios.

It currently doesn’t display the button as primary even though the variant prop is set to primary. If button group cannot be used in this scenario, I think the documentation should clearly state so.
It can be reproduced here: https://codesandbox.io/p/sandbox/44l4pd
In the real Shopify App, it sometimes works but not reliably.