In #11944 @TimothyBJacobs fixed the issue with behavior of TabPanel component by using Button component. Howeve, it introduces another issue described by @jasmussen :

It doesn't seem like we're using this component anywhere in Gutenberg itself. It really seems like it should come with some basic styles, and I'm essentially echoing @aduth here. This is because the Button component unsets the appearance and border of the button, so it's really quite bare.

But maybe that shouldn't hold up this PR if it fixes an issue? Not sure, and not sure how I can review this from a design perspective as there doesn't seem to be a design.

To put it more simply, if the above was the design we intended for the TabPanel component, it would not be shippable. But this could be a separate task, to improve that, as mentioned.