This has evolved over the years. See bug 1335018, bug 1343210, bug 1506503. The test for this is browser/base/content/test/siteIdentity/browser_identityPopup_focus.js. I guess this doesn't apply to the new panel?
Bug 2046307 Comment 4 Edit History
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This has evolved over the years. See bug 1335018, bug 1343210, bug 1506503. The test for this is browser/base/content/test/siteIdentity/browser_identityPopup_focus.js. I guess this test doesn't run for the new panel?