This sounds great but Google has been making it harder and harder to run your own mail server even for personal use. I think they would be happy of email servers were only run by a few large companies. They make it sound like they are doing the right thing but really they are bully the industry to do it their way. So many people have Gmail accounts that you can't run an email server that cannot send email to Google.…
I don't believe this particular change materially improves security, since it isn't representing an end-to-end behaviour, but if it raises awareness and challenges mass surveillance then so much the better.
Personally I would like them to advocate for other necessary infrastructure advances and include, for non-IPv6-capable MTAs, an icon of a lurching monster that refuses to die.