Apparently there is no way to mass delete photos once you store them in the iCloud Photo Library.
The documentation is only focused with being able to recover photos before the automatic deletion kicks in - not cleaning up content you want deleted now and permanently.
I've had a support request open to Apple Engineering since 20 March and they are either unable or unwilling to tell me any way I can bulk delete 7k photos and 31 albums. They've tried twice to clear my library - the first didn't do anything, the second cleared all but 15 photos. I suppose I might end up waiting out the 30 days and hope that everything truly goes away at that point.
I'm going to let the Apple support staff enjoy the weekend and then ask for more details from "Engineering" on Monday. My suspicion is that Apple designed tiered level of data storage (like sharding across "versions" or other similar mirroring) and are in effect maintaining two buckets of my iCloud data -- one for the non-Beta parts and another for the Beta parts. If so, they may have been a bit too clever with their schema and/or decided to not create the tools to easily rectify an edge case during the window of having two "versions" of iCloud photo data.
As I suspected, once Photos for OS X released with 10.10.3 engineering was able to delete things properly.
Even better, anyone can now delete an entire library by using Photos app on OS X:
- Open your Photos library that is the system library
- File -> Show Recently Deleted
- Select Delete All in the top right
- Repeat as often as needed if the app is still downloading new photos from the cloud