The GP's statistic is probably raw bytes, and yes, a significant chunk of that will be the big video streaming sites, which mostly have v6. That's still a useful statistic, because part of the cost of v4 is NAT and NAT capacity is measured in terms of number of packets.
I guess you're thinking that the number of v4-only websites is much higher than the traffic numbers represent -- which is true but that's actually fine because v6-only clients can still reach those sites easily via NAT64, so having a lot of v4-only websites isn't blocking deployment of v6 or undeployment of v4. The only real problem it causes is that people use it as an excuse to not do v6...
As for Google's stats, they're probably percentage of either connections or users as measured by their frontend load balancers.
I guess you're thinking that the number of v4-only websites is much higher than the traffic numbers represent -- which is true but that's actually fine because v6-only clients can still reach those sites easily via NAT64, so having a lot of v4-only websites isn't blocking deployment of v6 or undeployment of v4. The only real problem it causes is that people use it as an excuse to not do v6...
As for Google's stats, they're probably percentage of either connections or users as measured by their frontend load balancers.