Yeah, why? I have seen SO betas (e.g. ESSO (EsStackOverflow.SE)), but they haven't got any differences from normal sites (e.g. SO (StackOverflow.SE)) other than logos/icons/language. Why does this happen tho, and can it be fixed if it's wrong?
When we launch an existing successful site in a new language, what we're doing is expanding an established brand. The site is noted as being in beta only in the sense of "we're pretty sure everything works, but please don't think too poorly of us if something fails to meet your expectations." Hence, we use the design of the established brand.
When we launch a whole new topic, no one is really sure of what the outcome will be. The Area 51 process gives us some assurance that the topic will work in strict Q&A format, and that we appear to have enough interested people to pull it off - but sites sometimes fizzle out or fail to really define their scope in the world of Q&A. Creating a formal design is an incredible amount of work, which is why sites on new topics start out with a standardized neutral design.
In essence, if we launch Chemistry in another language - that new site will look just like Chemistry in English, except not in English - as Chemistry would be a brand being offered to a larger group of people.
Note: We have no immediate plans of launching sites other than Stack Overflow in other languages, I was simply making an example :)