According to an anonymous redditor, the so-called “confirmation” of Google’s Project Hera with Gmail hails from the screenshot that you see on your right. It does seem as though the post was put up using a throwaway account, so it remains just about impossible to follow up and get any more additional details. What we do know, however, is that the post specifically mentioned that “Project Hera is real, but AP leak is not.”
This post also failed to shed any light on the theory surrounding HTML5 functionality integration being accurate or otherwise, but it does mention that the mock-ups which were posted were inaccurate. Citing “proof”, said redditor put up a picture of a development version of a Gmail redesign in the works. We would advice everyone to just be extra cautious about whatever is being shared concerning Project Hera until something official comes out.