OKI C931 and spot color kit - convert to a C941

So, I know that spot color is only available for the C941. But when I check the printer, one can actually put a spot color kit into a C931.

Therefore, I'm wondering whether the difference between the C931 and C941 would only be software (firmware).

However, I can't find any such use cases describing this. Either no one bothered, or no one tried, or tried and failed.

 

The C931 is a four toner printer and the C942 is a five toner printer CMYK+spot so there is no slot for a spot tone and drum in the C931 printer