Say all is not a proper description of the NVDA key down arrow command.
That command doesn't say all unless you start at the beginning of a
document. It starts to speak or read, from your current position in the
document. Also, say all sounds like an adjustment in screen echo. The name
should be changed to something like read to end, or speak to end. I don't
use a Braille display so I don't know if the command would be used there.
If not, speak to end would be best.

Gene