Got the registration for the test done, ostensibly. We'll see whether they actually let me take it without the high school diploma. It looks like I probably won't actually know this until I sit down to take the test and the proctor checks the documents.
It’s *possible* I can register for the exam without it, especially since I’m 90% sure my UCLA transcript (which also must be uploaded) does acknowledge that I graduated from a California high school. I’ll check and see once I get back to where I’m staying.