The keynote was for consumers and the press. The 2 PM PT Platforms State of the Union is for developers and will likely go into this more, and if not there is a session tomorrow specifically about it.
Still... Marketing fully-encrypted snapshot-featured filesystem with focus on SSD / Flash, would make much more impact than having "native-tabs" for apps on an event like that.
Anyway I'm not a specialist, just another IT guy, so maybe I'm too opinionated to argue more.
The press understands "apps" and "tabs". The press doesn't understand "filesystem snapshots".
Part of the reason Apple has historically gotten much better press from WWDC than most tech companies do from their big developer events is that they laser-focused their keynote on being Press-digestible and not full of incomprehensible tech terminology that bores non-geeks to tears.
As evidenced by this thread, the people "filesystem snapshots" can be marketed to didn't need it to be mentioned in the keynote to get them talking about it. Hence, using precious keynote time for it would have been a waste of marketing resources.
I don't think this is going to be a part of macOS Sierra as a standard feature, given that it has a release date in 2017 while Sierra will be out later this year. So it makes sense to not include it in a Sierra announcement.
