The Scottish culture as far as this time frame is concerned is Gaelic. There are non-Gaelic speakers in mainland Scotland, such as English in Dunbar and Teviotdale provinces, adding perhaps Lothian and Clydesdale from the later twelfth century, and Norse in a bit of Caithness. But these guys are not regarded as 'Scottish' by the people of the era, and the territory is outside of 'Scotland' (as opposed to the territory ruled by the king of the Scots). Scots are Gaelic-speakers living in 'Scotland', i.e. Britain north of the Forth river. People in Galloway, Carrick and most of the Clydesdale province c. 1066 are also Gaelic speakers, but are not regarded as Scots, but rather Galwegians or Gall-Gaidel.
The game uses an anglicized Gaelic list with a few Anglo-Norman or Anglo-Saxon additions, and abstracts all the people of the territory of Scotland into one culture. If that's what the devs want to do, then that's their right; though it is not accurate to claim that this is because of a general policy of anglicization, since other than the Scots and Normans, lists tend to be 'native'. On the other hand, ethnic names tend to be in line with whatever the language or orthography of the modern country is, with the notable exception of Ireland, the 1066 Normans and some of the Turkic regions, and modern Scotland is for the most part English in speech not Gaelic. Still, not sure if people will be quite as tolerant about about Scots named Walter and William in the 9th century ... though the Irish list has many Anglo-French borrowings too, and most other cultures will have similar problems with anachronistic borrowings.
The issue with maitaining a mod is not only would you need to maintain all changes in the Scottish file, you'd also need to do this with the Saxon, Norman and English files since there are characters in the Scottish file who, were the culture used historically, shouldn't be so (Anglo-Norman immigrants, and Anglo-Saxons ruling territory that happens to lie within the boundaries of the modern country).
Do note however that the abstraction issue and the anglicization issues are separate. It is possible to have a Scottish culture with a time-appropriate list of anglicized names used by Gaelic speakers even if abstraction were abandoned.