It is end to end but CloudFlare does not verify the identity of the origin server. The only equivalent option would be "Full SSL (Strict)", which is not free.
That is simply untrue. Full SSL (Strict) is available on all plan levels including free. There is no charge for it. In addition, if you don't have an SSL certificate on your origin we'll give you a cert for free as well: https://blog.cloudflare.com/cloudflare-ca-encryption-origin/
I believe Strict SSL is free on Cloudflare's side, but GitHub Pages does not work with it because it does not present a matching and valid certificate.
