So since there's still been no official word back from Amazon, I just sent them a carefully-worded ping asking if there was any news for me on the outcome of the interview, which they'd promised in 48 hours.
"...I felt the interview went well, although given the nature of the position I was a little surprised how few of my interviewers actually went into any technical depth...."
We've already had unofficial word back that the manager thought I wasn't technical enough. The objective here, I'll be blunt, is to get them to consider, "Maybe the reason I didn't seem technical enough is because you didn't ask enough technical questions...."
Worst that can happen at this point is it doesn't work.
Update, five minutes later
Gee, that was fast:
Hi Phil;
Great to hear from you. I tried to call you yesterday but failed to reach you. I hope your trip home was a safe one. At this point the team has decided to pursue another candidate for the role. They felt you were strong but have a candidate who appears to be a closer direct match to the role you interviewed for. That said, I will place your resume back into the database for other managers to review and consider. If you have any additional questions please don't hesitate to ask. Thanks for your time and my apologies for not making contact with you sooner.
So, still a "no", but not as negative of a "no" as the unofficial word first made it appear.