I just experienced this too.
Version 68.0.3440.84 on Mac.

I was on the page
http://jakehofman.com/inprint/best_perspective_chi2018.pdf
and clicked on the link to the nytimes article on the first page of that PDF, and zero suggest opened on top of the new york times page.

I cannot get it to happen again.  (That said, I haven't restarted my browser.  Maybe that would help repro?)

krb: As the person cursed with knowledge about our elaborate focus behaviors, would you mind giving some thought as to whether there's some code path that could cause the omnibox to be focused on page load, thus triggering zero suggest? Given that we don't know how common this is, no need to spend a lot of time on it. I'm just hoping you can come up with some hypothesis as to how it's happening.

I also use 68 on a MacPro occasionally, but I spent some time clicking on links, and I couldn't duplicate it. The closest event was the pop-up for the site wanting to show navigations.

There are calls to change focus in the navigation path but I believe they are all to focus the content area. I'm wondering if something else is going on (like a phantom click). I also tried "accidentally" pressing modifiers while clicking. They open the tab in the background, download the page, bring up a menu, etc. but nothing unexpected.

My best guess, having seen this once (hah!), is that it has to do with focus already being in the omnibox, and clicking on the page, and maybe a race between the navigation / context area gaining focus and the navigation actually happening.  Maybe if the focus is still in the omnibox at the time of the navigation, the zero suggest dropdown will open?

But you said, "I was on the page... and clicked on the link." Are you saying that focus was instead in the Omnibox and you clicked the link? Otherwise focus shouldn't change (afaict, still looking).

I was on viewing a page.  However, I was switching tabs regularly at the time, I think while constructing a query in the omnibox.  When I have modified temporary text in the omnibox (with focus in the omnibox), switch tabs, and switch back, the temporary text remains and the omnibox is in focus.  The dropdown is closed.  Then I click on a link in the page itself.  I think that might've been the kind of thing I was doing at the time.