I’m no SEO guru, but I’m curious: what’s your real concern here? The speculation technology itself? Or the mere presence of the /cdn-cgi/speculation URL (and it’s potential impact)?
So if you’re concerned about these URLs getting crawled and/or indexed by search engines, then the simple solution is to add Disallow: /cdn-cgi/ to your robots.txt file to exclude this path.
It will most likely improve your SEO, since speculation will tell the user’s browser which files and pages to load next, resulting in a faster browsing experience, which is part of Core Web Vitals.
Beware that even Wordpress is implementing this in its newer version, so, even if you disable it at Cloudflare’s side, it could still trigger at your Wordpress’ side. But for real, except if this is causing an issue, don’t deactivate it in either side. You’ll lose more than you’ll gain.
