Sorry for the confusion, there are a couple things going on here and I will do my best to clear them up!
The ideo.com website itself is not hosted by Webflow. (However they do use Webflow for many other of their sites, such as https://www.circulardesignguide.com/ or https://antibotics.ideo.com/)
As for the other sites, whether or not they use Fastly depends on whether or not they are using SSL. Fastly does not (currently?) have support for automatically provisioning SSL certificates for a domain, so we were not able to use them for our SSL hosting infrastructure. Instead we have built our own infrastructure for handling SSL connections on top of AWS. This currently is limited to a single region (Virginia) but we are actively working on support for multi-region SSL hosting and should have updates on that very soon.
For sites which do not have SSL enabled, those are using Fastly. The distinction mostly occurs at the DNS layer, so if you point your domain to
proxy.webflow.com it will use Fastly. If it is pointed to
proxy-ssl.webflow.com it will use our own infrastructure to handle the SSL termination.
Let me know if that didn’t clear things up or if you have other questions!