I should point out that this "news" is a couple of years old and I cannot understand why Y Cyngor Abertawe (Swansea Council) could not have done it in house at that time.

Mistakes are rare but everything should be proof read and checked before a sign is made, not afterwards.

Where a language that is native but not given at least official support and overwhelmed by the usage of another language, then that language is in danger of dying. There are native but minority languages all over the place and it might be amusing to see goofs that can in any case happen in many kinds of translations but the exceptions do not prove the rule.