We're waiting for an answer from the Product folks about the intent of this design. The tiny amount of the URL that shows would reveal the site, but not any content details.
Bug 1780842 Comment 10 Edit History
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We're waiting for an answer from the Product folks about the intent of this design. The tiny amount of the URL that shows would reveal the site, but not any content details. Wouldn't it be easier to blank the whole screen than to exempt the toolbar part? That's what makes me wonder if this approach is intentional.