pak64 and base are more or less maintained like that. For german translation is even forbidden for base.tab. But given the many other pak set developed since then as well as languages I cannot judge at all, translator is not worse than receiving list from people I do not know either. The other reason is that we simply do not have translators for several languages for many of the new entries since then. If limited to devotees, simutrans would only come in seven languages (italian, portugese, french, english, german, japanese, and spanish).
In the end I have to trust somebody. For instance the korean translation was made from the japanese one, as the translator was not really speaking english. Thus I did not know the person before, he just mailed part of the translation, finished it an vanished. Repeated process with other languages.
The translator also helped and found many broken entries and helps to keep translation files current as well as indicating missing translations. A task almost impossible, when maintaining everything by hand. The original files had more than 100 missing entries, most unfamous "Die Brücke ist nicht frei" which prevailed for several years.