Google said that when it publishes content on its sites, like the developer documents (or maybe even blog), it requires a code push for it to deploy on the site. That does not surprise me at all that Google does not use a CMS platform for this part.
This came up in the last Search Off The Record podcast where John Mueller so elegantly segwayed into the topic that Lizzi Harvey, a Technical Writer at Google on the Search Relations team, was on the podcast for to discuss.
She explained that the process is that someone normally writes a draft in a Google Doc. Then that Google Doc is converted manually to HTML. That HTML page is submitted to the team that manages the page for code review. But she said for the sites she maintains it is more streamlined, she said "So, all you do is submit to the code base and then it pushes it like within a second. So, you just click a button Submit and then it's live."
This part of the conversation starts at the 18:04 mark into the podcast:
Did you know that these blog posts are all written in HTML? I do not use a WYSIWYG editor of any kind? But this is a crude and old CMS, so not real code pushes are needed for me to publish content here.
Forum discussion at Twitter.