It's "JSON", which is a data syntax.
Yes, sdcv does a fallback. And to be more exact, it is a levenshtein distance based search. That will always have it drawbacks. But then, it's what sdcv offers. sdcv is upstream code and isn't likely to implement more features soon (I guess).
I started an implementation of a stardict dictionary parser in Lua, but it's in no way finished and it will still need considerable development to bring about something useful with it.
@CaptainD: Can you file an issue for this in
https://github.com/koreader/kpvbooklet ?