Nice guide, some of the information seems outdated or incorrect though. I know that Proton and Tuta have their own apps (and even require them to be used afaik). Proton also has a surrounding ecosystem with a VPN service etc. Same does for them having a free tier. GMX belongs to its sister service web.de, which is not on the list but which is functionality almost identical, and both of them also have their own apps.
So the classification on the right seems a little arbitrary.