Maxim,

You're indisputably right -- the IETF RFC (which I should have been using in the first place) clearly states that compliant HTTP 1.0 clients "understand any valid response in the format of HTTP/0.9 or HTTP/1.0," and that HTTP 1.0 responses can be be in the form of a status-line-less "simple response." In light of this, nginx does strictly conform to the specification in this regard.

I owe you an apology for wasting your time by not being more thorough in my research, and a "thank you" for taking the time to correct me!

Cheers!