Whenever the HTML that’s rendered in your browser contains some personal information (e.g. an email, your legal name, whatever), it would be included in the archive page and signed by you. If you are not really really careful about what the extension includes in the page, you could leak information that you don’t want to share. The same with stuff that might not even be visible to you. Imagine a newspaper that has a profile page modal for logged in users. The modal is part of the HTML, but hidden via css until you open it. HTML scrapers would still include all the data that is part of the hidden model, without it ever being visible on the users visit