I'm guessing that the auto-respond was written in both languages, but somebody forgot to read the English bit and just copied down the bit that looked Welsh.
Of course, if these people were rational they might take a step back at this point and say "If Welsh-speaking skills are so rare here in Wales that this kind of thing can happen, why are we bothering to translate everything into Welsh?"
I think it's because they're politically pressured to; there are cultural groups trying to keep the Welsh language from dying out. (I don't know Welsh or live in the UK, though, so I'm going to defer to anybody who knows better.)
Maybe a better observation is that if you're the only person in a company that can read/write a language, don't write your auto-respond message in it.