If a program’s behavior is undefined in one specification and defined in a second, then insofar as both specifications apply to it, that is defined behavior, not undefined behavior. That’s not an obscure property of terms of art and specific formal definitions about which I need to be educated, it’s just basic logic about which we obviously agree. The conclusion would be the same if one specification explicitly said “this may return an empty allocation or NULL or format your hard drive” and a second specification said “this will return an empty allocation or NULL”; the conjunction of those two specifications entails that it will not format your hard drive.

There’s nothing wrong or misleading in what I wrote. If, hypothetically, there were a second specification that constrained the Rust compiler’s translation of programs that over-read memory, then it would have been wrong to write that over-reading memory in Rust is undefined behavior, and misleading to suggest that a statement about “any undefined behavior” is applicable to it. But there is no such second specification (as confirmed by comments on the issue I linked from RalfJung, whose formal specification hat is much pointier than either of ours), and you aren’t even disputing that. Instead, you have deliberately misapplied a statement about “any undefined behavior” to other unrelated behavior that is in fact defined, in order to construct a pretense for calling someone else dishonest. Find better hobbies.