The base requirement is that the device/service is accessible so we should be clear that a non-natural language alternative that fulfils an accessibility need is acceptable.
I suggest changing
"REQ 4:Support multiple output devices and methods."
to
"REQ 4: Support multiple output devices and methods either within the natural language interface/s or via alternatives."
The base requirement is that the device/service is accessible so we should be clear that a non-natural language alternative that fulfils an accessibility need is acceptable.
I suggest changing "REQ 4:Support multiple output devices and methods." to "REQ 4: Support multiple output devices and methods either within the natural language interface/s or via alternatives."