Disclaimer. I am the author of Hugo and former exec at Docker. I don't speak for Docker and I've been gone for over a year so the following is at best a guess.
From my reading of their blog post I see that their primary motivation for the change was first to consolidate all of their documentation into a single repo, instead of spread across all of their various projects. As they have grown as an organization and now have a large number of projects this approach has a lot of strengths and makes a lot of sense. Any SSG could work in this new formation, but the change gave them an opportunity to make a change. Additionally Github provides a lot of Jekyll features out of the box that help with managing these documentation sites.
I believe it is not a question of performance between Hugo and Jekyll, but a question of Docker's specific workflow. As Github already runs Jekyll server side all the contributors need to do is upload the source file and then Github does the rest. In contrast, Hugo based docs would have to be built locally and then uploaded as completed html. There are easy ways to set up services through github hooks that do the exact same thing as Jekyll already does but that requires additional setting up.
Since Github is doing all the work it is easier on the contributors since all they need to do is `git push`. This also enables people to edit right in the github edit screen and not bother with setting up anything client side. The total time to process the site is likely much longer on Jekyll but the time that their contributors spend is much less as they aren't building the site locally.
From my reading of their blog post I see that their primary motivation for the change was first to consolidate all of their documentation into a single repo, instead of spread across all of their various projects. As they have grown as an organization and now have a large number of projects this approach has a lot of strengths and makes a lot of sense. Any SSG could work in this new formation, but the change gave them an opportunity to make a change. Additionally Github provides a lot of Jekyll features out of the box that help with managing these documentation sites.
I believe it is not a question of performance between Hugo and Jekyll, but a question of Docker's specific workflow. As Github already runs Jekyll server side all the contributors need to do is upload the source file and then Github does the rest. In contrast, Hugo based docs would have to be built locally and then uploaded as completed html. There are easy ways to set up services through github hooks that do the exact same thing as Jekyll already does but that requires additional setting up.
Since Github is doing all the work it is easier on the contributors since all they need to do is `git push`. This also enables people to edit right in the github edit screen and not bother with setting up anything client side. The total time to process the site is likely much longer on Jekyll but the time that their contributors spend is much less as they aren't building the site locally.