That may imply Python 3 earlier than 3.7 was on GAE, which is not the case.

perhaps, but python 3 is quite vague and 3.7 is very different from say 3.4. Saying it is 3.7 is of significant interest to me.

Any highlights of why 3.7 is significant vs 3.6,3.5,3.4?

If I had to guess, I'd say the most relevant changes for App Engine use may be the optimizations documented at https://docs.python.org/3/whatsnew/3.7.html#whatsnew37-perf : the `sort` method of lists about 50% faster in common cases, the `copy` method of dicts up to 5 times faster, etc.

Yes, on these pages: https://docs.python.org/3/whatsnew/3.5.html .

Of significant interest to people who are stuck/like writing Python would be the async changes in 3.5 and 3.6. There have also been constant type annotation enhancements made throughout the 3.x releases.

Speaking for myself: 3.7 is the newest release with all the nice shiny, new features. Knowing that I could actually use the most current tools makes AE much more attractive than it was before this announcement.

It took them so long, I think pointing out that it's 3.7 emphasizes that they're finally caught up.

In the context that it's taken them a decade to upgrade, just seeing "Python 3" makes me wonder if they're only supporting some ancient version like 3.4 or even 3.2.