Then this is a half-baked solution to the problems caused by making tabbed browsing hard.

On the desktop, I will open a bunch of tabs and close the ones that don't pan out. Not just after a Google search, but after anything resembling a search.

Mobile browsers allow this (though slightly awkwardly), but most mobile apps which display web content don't allow anything like this.

Do you think that it how most people search? (I'm not being sarcastic, I doubt they do but I obviously don't know)

I think it is the way most people who care about trying out multiple hits do it. For everyone else, the back button is good enough.

Given that landscape, what is added by a fat page wrapper that makes it easier to go back to the search engine?

But how much of that is in response to slow load times, and optimizing viewing the results without waiting? If AMP is fast, then whatever portion of the reason to do this was caused by slow loading is significantly reduced.

Also, in regards to your up-thread comment, on mobile browsers I will sometimes use that technique because (but only because it can be slow to wait for multiple to load), but doing so is generally more cumbersome. Hold on link, select to open in new window. If I could just quickly visit each as needed, returning if it wasn't what I was looking for, I would much prefer that (as opposed to on desktop, which while I would like quicker loading, I do still occasionally want to open multiple tabs for results as you suggest). That is, I don't think this is a half-baked solution to a problem caused by making tabbed browsing hard, I think it's a solution that addresses some of the reasons we use tabs in the first place (specifically, to parallelize loading times for possibly slow sites).