It's not that either, and you are validating the GP's point. Rust has a very specific 'unsafe' keyword that every Rust developer interpret implicitly and instinctively as 'potentially memory-unsafe'. Consequently, 'safe' is interpreted as the opposite - 'guaranteed memory-safe'. Using that word as an abbreviation among Rust developers is therefore not uncommon.

However while speaking about Rust language in general, all half-decent Rust developers specify that it's about memory safety. Even the Rust language homepage has only two instances of the word - 'memory-safety' and 'thread-safety'. The accusations of sleaziness and false accusations is disingenuous at best.