aria-expanded and toggles content with hidden.
The quick summary looks fine visually, but the “Read more” control below is just a styled <span>. It can’t be reached with Tab, so keyboard and some assistive-tech users can’t expand the text.
The preview is short, and the “Read more” control is a real button.
When expanded, the extra text becomes visible and is part of the accessibility tree. The button exposes its state via aria-expanded, and the expanded region is linked with aria-controls.