It is fixed in macOS 15.1 beta 3. Voiceover now reads the element that receives aria-activedescendant if I navigate using the arrow keys. The problem is that widgets that rely solely on aria-activedescendant are less likely to work with the Voiceover cursor, and the Voiceover cursor is the primary form of navigation for most Voiceover userss. While a pattern like the select only combobox in the aria authoring practices works seamlessly on Windows where screen readers automatically switch off virtual mode by default and pass the keystrokes to the browser, it is likely to be perceived as an inaccessible combobox by Voiceover users who primarily rely on Voiceover commands to drive the UI. In any case the bug is fixed, and that is great news.