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You are making a subjective judgement there. I *do* want to see the actual scene colours at the time; it is part of the creative process. I want to be "immersed" in the scene - it is why I use SLRs.
OK; that's fine. I don't mean to imply that viewfinder color accuracy shouldn't be important to you. However, your original question about how "no-one ever mentions colour accuracy and gamut" almost answers itself --- for a majority of current SLR users, who might become future EVF users, this is a secondary concern to more common issues (ergonomics/focus speed/etc.). For guessing how Canon, a camera maker catering to the general majority of SLR shooters, is going to transition to future technologies, it makes sense to primarily consider the "common" issues with mirrorless cameras, rather than the niche concerns of a few specialists. Just as some people still love shooting large format film, yet Canon doesn't sell 4x5 cameras, Canon is also likely to move ahead with mirrorless cameras regardless of the occasional specialized concern.