63 zones vs RGB metering

In the 7D, Canon deployed a metering system consisting of what looks like 63 individual dual layered sensors which makes up the 63 zones metering.

On the other hand, Nikon has been using the 1005 pixel RGB sensor for metering as well as AF tracking. It seems like Nikon uses the same sensor for AF as well, instead of a separate AF subsystem like Canon.

Having 63 different sensors seem like a much more complicated solution than just having one single RGB sensor, like what Nikon did. Canon has stuck to this design for years and I am sure there must be a reason for them to do so. Otherwise, I thought the single RGB sensor approach looks like a much more scalable implementation. Making a 1000 zone sensor would be really a challenge for the Canon approach.

As with any engineering designs, there must be some pros and cons for a particular approach. Does anyone in this forum know the true advantage of the 63 sensor approach over the RGB sensor approach? One advantage I could think of may be speed but perhaps someone more familiar with the metering system can enlighten me a little.

Thanks.