It's not sneaky just because you're not looking. I have found the CoreOS group to be guarded in their responses to future directions but never sneaky. There have been multiple times where an API/design/etc change in a WWDC session didn't make sense. I would follow up in the labs and be told the reason is because X is happening in the future. Granted I'm not always told. In that case a diff of kernel sources between releases along with some years working in the XNU kernel is enough to figure it out. Sometimes you're just lucky and hint it in the actual session. For example the 2013 WWDC Session titled "What's New in Kext Development" (https://asciiwwdc.com/2013/sessions/707) leaked SIP well before it was officially announced. They key line was:

So in the future, we are going to tighten down access to the system hierarchy, the whole hierarchy down from /System and everything in there.

Another example of them sharing future plans was user space networking. I forgot what year it was but in the session they noted something about network kernel extensions (NKE) going away and to use Network Extensions instead. NKEs weren't the best but for Apple to send all the effort to recreate the 'same' thing in a new framework was odd. A visit to the labs and you were instantly told of the move to user space networking.

One last example. Apple ships in the default OS a number of third party mass storage kernel drivers. Take a look at /Library/Extensions on a new install. This ensure when you try to install that new OS or boot that new OS, you can see you're drives. Apple likely needs to work with those third-parties to make that happen.

I understand why it might appear sneaky but I don't think that's the case.