I was just wondering if it would make any difference, doing it before or after, but I think I don't know enough about how the debayering is actually done.
I suppose that if manufacturers don't share the spectral responses of the channels then no-one can know what the primaries are, so although they'll know the gamma is Linear they won't know the colour space. Therefore if they want to make the image more warm along the neutral axis, they'll be boosting red and green but won't know the correct proportions to move along the right vector (unless they do some testing to determine this).
I guess it's a situation where you have all the usual suspects feeding into it, like corporate secrecy and paranoia (in the guise of "competitive advantage") and poor understanding of transparency and the benefits of open standards, but also poor business management and inability to understand how the customer experiences their products. Industrial espionage is also something that happens and there's a balance between being transparent and making it easy for your competitors to undercut you in the market.
I think for ARRI the marketplace might be somewhat different, but perhaps not. Then again, ARRI got sold and not all the Japanese manufacturers needed to be put on the market, so maybe their curmudgeonly ways paid off...