So, from my perspective (which obviously is tied to my location) is that all computers have IPv4 (haven't heard (and I've asked) of a single consumer ISP that offers IPv6) but all mobile phones have IPv6. Whether people in general do most searches on mobile or PC is gonna change that graph dramatically, but won't explain what I would be interested in regarding ipv6 adoption. That is, how much of the world would be broken without IPv4?
And for that, that graph isn't completely useless - but not too far off.