The chart has the reader's focus, and the page has the browser's.
What their screen reader last spoke for their position, or null.
OptionalblockedA MAIDR dialog or text field (chat, settings, help, braille, review, ...)
holds their focus, so a move now would not be one they could make from
the keyboard. Absent reads as false.
Where the reader is in a mounted chart, as LiveReaderProbe reports it.