Just pains me that the Rust team is so oblivious to the fact that they need a spec if they ever hope to have a chance to replace C.
C did not have a standard for 18 years, it was first created in 1972, and ANSI C didn't appear until the spring of 1990. I'm not suggesting that it took them 18 years to write a spec, it's that it wasn't really needed for a long time. Expecting Rust to have one after five years is aggressive. Some languages have done this! I think we'll end up somewhere between what C did and what C# did, in this regard.
However, you do also bring up something that's a good point when it comes to this discussion: a lot of people treat "a spec" as a binary thing: a language has it, or does not have it. But specs are written by humans, and have their own mistakes, bugs, errata, etc.
One of the reasons that we haven't wanted to declare "this is the spec for Rust" is that we want to have a good, possibly even formally verifiable spec. The reference is basically at a fairly reasonable informal spec level.