The number of Welsh speakers who don't speak perfectly good English
also approaches zero, but I don't see that they're likely to go along
with this approach either. Nor should they be expected to - "in their
own language".
Different situation. Scots Gaelic is only really relevant to a fairly small percentage of Scots. For most their ah not English would be lowland Scots which on a practical level merged into English about a century or so ago.