I think it is worth to mention that the Google stats don’t measure China adoption, which clearly accounts for a big % of the Internet, and is progressing very fast. If google could measure that, probably we will discover that in reality we are pass the 65-75%.
Also we need to understand that the bigger content providers and CDNs (Meta, Google, Akamai, etc.), have deployed IPv6 and their traffic usually accounts for the biggest chunk of the total Internet traffic. In addition to that, because those content providers and CDNs have caches everywhere, measurements in IXs (for example), only can measure once a video, update or whatever, which is downloaded by ISP customers many times. So a more ISPs are deploying IPv6, the effect of real IPv6 traffic to the edge is much bigger than what we are actually able to measure and verify.