I don't think it's a secret. Google's been pretty open for a while about the fact that they want to get rid of URLs entirely on the web.[0]
De-emphasizing the URL in search is a necessary step on the path to that end. The less of a role the URL plays in ordinary people's lives, the less that people will understand it, and the more evidence Google will see that it can be de-emphasized in other places, and eventually removed or replaced entirely.
And to a certain extent, I get it. I myself would like to move away from URLs to a DAT-adjacent system. I'm not fond of DNS as it works today. I just think Google's approach to all of this is naive and user-hostile. I think their solution will be worse than the problem.
Proponents of DAT systems are advocating that URLs as we use them today aren't great for a lot of stuff, including protecting against phishing, and we should be more up-front about that and stop aiming for readability in domain names -- in short, don't promise something that we can't guarantee. On the other hand, Google is advocating that there should be centralized authorities that tell you Walmart is Walmart and everything should be highly tied to trademarks and brands. Their position is, "phishing won't be a problem because we'll just get good at blocking phishers." When you search on Google for Walmart, it'll be the first result and you'll click on it and trust Google.
It's a very centralized, brand-first, Capitalist approach to the web, where reliability is tied to being big enough that you can tell potential customers or users to just Google your name.
Sometimes Google does bad things and we theorize that maybe they're trying to change the web; but in this case we don't have to theorize. They're just openly trying to change the web. Google doesn't like URLs.
[0]: https://www.wired.com/story/google-wants-to-kill-the-url/