This is most likely a check that Netflix is doing on their website, as the language changes automatically when I access through a VPN. Here I'm accessing through The Netherlands and the language changes to Dutch automatically, although the cookie consent modal still appears in the system-set language, which is French.
The same is true if I change my location to other regions. However, other websites are able to detect and respect my language settings e.g., qwant.com.
You can see a similar issue in this thread, where the only solution was to spoof the user agent to appear as if the machine was using Windows. Not the best solution, but ultimately this is on the website developers themselves to respect or not the user settings.