HN user
I think that the main reason is exactly what the author mentioned on his conclusion:
"Perhaps the way IPv6 deals with additional headers in contrast to IPv4 may be influencing this difference. This stability is observed most evidently on sucuri.net and cloudflare.com. Interesting, as both domains deal with web security."
Not sure how, but Joomla, WordPress and other CMS's need to find a better way to improve their security features. It is hard for me to believe that a "high-severity vulnerability that allows remote users to create accounts and increase their privileges on any Joomla" it was just missed all these years.
A good code review needed to find this.
"Interestingly enough, despite the need for more IP addresses, only 33% of the top 100 sites in the world have IPv6 enabled. Big properties like Bing, Twitter, Live, MSN.com, Amazon, Paypal, WhatsApp, Dropbox, and many others do not support it."
I was under the impression that this number would be bigger.