Q: Why do cultures not correspond to language families in all cases?

A: Our culture groups are a combination of heritage, cultural similarities, and a result of both history and areas of influence. Language is one of the tools used to discern this and we look both at language families and sprachbunds.
For many examples here it has more to with dividing the culture group; thereby, preventing culture unions.
Such is the case for the regional culture group Caucasian & the more culturally based Cushtic (Some languages in that group are actually Semitic).

Q: Why are Sardinian, Maltese, & the Rhaeto-Romance Languages in the Italian culture group?

A: Well this is because it is called Latin not Italian, while linguistically it may make sense to differentiate these, a shared cultural identity does link these cultures to Italy and dividing the culture group numerous times for just one culture that is different in regional and linguistic ways alone is unnecessary.

Q: Why is Altaic in the game?

A: Altaic in the game is basically a stand in for Turco-Mongolian. The two are very culturally interconnected. The Altaic larp beyond Turco-Mongolian is what has been debunked more, Turco-Mongolian themselves actually do share a great deal in common and had Urheimats near one another. Turkic leaders pointed to Genghis Khan as a predecessor in fact. Renaming this or dividing this group may be considered in the future.

Q: Why is Etruscan Latin & Basque Iberian?

A: Firstly, they are culturally interrelated to those groups, despite being distinct especially language wise. Secondly, having them in those groups allows for a cultural union and access to the options and trees of those groups.

Q: Why is Albanian in Byzantine?

A: Albanians are alone in their branch of Indo-European Languages, they are theorised to be derived from Illyrian people and languages, making them pre South Slavic, not South Slavic. Additionally, they had close historic ties to Byzantium such as the noble Muzaka family of Albania.

Q: Why is Gothic Germanic?

A: Crimean Gothic actually had a disputed amount of West Germanic influence and it is the best fitting culture group all things considered, making it its own would not change anything.

Q: Why is Silesian soo small in 1444 & why is it Germanic?

A: Silesian should really be two different cultures, one being Slavic Silesians, and the other being German Silesians. They are often confused and their histories are interwoven, but they are still regarded as distinct. The Silesians we know of that use the flag of the primary nation (Silesia) and take up the majority of the timeframe of eu4 are the German ones. That said I made Polish and Slavic Silesian provinces Polish until the appropriate year startdate and Opole accepts Polish just the same.