Steps to reproduce the issue

This is a bit tricky to observe but the easiest way is to go to /administrator/index.php?option=com_messages&view=messages and select options

Inspect the source and look for the first (only) occurrence of <section>
it will look like
<section id="permissions" name="Permissions" aria-labelledby="tab-permissions" aria-hidden="true" role="tabpanel" active="">

As you can see it is the active tab BUT it still has aria-hidden="true" it shouldn't

If you repeat this with other tab sets in the options for other components then you will see that onload and with no cookie set the first tab has the aria-hidden even though it is active. As soon as you click to another tab then that new tab will have the aria-hidden removed etc

The problem is on the first load only in that the initial state of the active tab is including aria-hidden when it should not.

I believe this is related to the tabs custom element.