Wouldn't "until today they have produced six" be translated as "hasta hoy han producido seis" with no se? The se would make that reflexive. But producirse means to take place, not to produce something. E.g. "Las elecciones ya se han producido" means "the elections have already taken place."
You're correct on your first point. Unfortunately this seems to be another case where enough people have reported an incorrect translation that DL now accepts it anyway.
This is neither reflexive nor the impersonal 'se,' though. It is the passive 'se.' The 6 didn't produce themselves (I don't think) and the impersonal 'se' is only used with a 3rd person singular verb ('ha' not 'han'). (http://www.spanishdict.com/topics/show/87)
Reflexive pronouns like se are often used to convey things like "they produced themselves"
But the use of "se" for the passive voice is different.
This sentence means "they were produced" -- what makes this passive voice is the "se". There is no mention on who or what produced them, just that they were produced.
They were produced by the company (i.e. the company produced them is the active voice way to say this)
This sentence does not imply that "they produced themselves" It's passive voice.
"Se habla español" - does not mean "spanish speaks itself" it means "spanish is spoken"
Again, SE is damn confusing! Just when I think I understand its usage in certain situations, I get confounded by its use in seemingly different sentence structures. Is the use of SE to show that "Seis" is the subject? I thought SE shows that the action is happening to/on the Subject. Other times it seems to show that there is no defined Subject, no he/she/it/you. Confused???