Q&A announces the displayed content as well as the screen reader only content.

When the screen reader encounters the the Q or A it reads "Q [pause] question" or "A [pause] answer". Screen readers will read pseudoelement content if they can and there is not a reliable way to do this in a cleaner way than having actual elements for the visual element and screen reader content and controlling their visibility.

There is a technique for giving ::before content an alt text but it is not well supported