[co0nsta]

How do you define "actually leaving"? Because after navigating to the portal, it occupies the whole viewport and becomes the main document with your site's URL.

Even if we assume you use AMP, package it with signed exchange, and Google SERP displays it then, yeah, your site could appear with no extra network request to your site. The lack of network requests isn't that different to old school HTTP proxies but with better specs and security. AMP has analytics and stuff so if you want to count visits, go do that.

I think the problem these technologies are meant to solve is making navigating between pages take under a hundred milliseconds and appear much faster by being able to preview/animate them. That would be good.

Yeah, new technology is not without cost and risks but Google turning the web into a walled garden isn't high on my list of risks.