It's not a lie. Terminology has nuance, and its meaning may change based on context.
1/ It says on the tin "prevents segfaults". It does not prevent segfaults in all cases, but OK, let's debate the other claim.
2/ It also says "guarantees thread safety". What is the Wikipedia definition of thread safety? It varies, so let's take the most common "freedom from race conditions."
Steve come and say Rust can have race conditions https://news.ycombinator.com/item?id=13376485 and that it's a common misunderstanding to think it prevents race conditions. Surely it would be great if the frontpage would not promote it!
Ergo the frontpage claim is false.
The wikipedia definition is pretty vague, it relies on a concept of "safe" that isn't defined there. It's acceptable to say that "data race safety" is "thread safety", though confusing. Rust's homepage does clarify what it means in the bullet points below that statement, so I wouldn't call this a lie. It may be misleading though, and this is a common misunderstanding as steve mentioned, so I submitted a PR to fix it https://github.com/rust-lang/rust-www/pull/685
In the punchline, "prevent segfaults" is framed in negative terms. If you put "provides memory safety" it will be a bit less evocative of specific pain, but will give a warm feeling.
Not too sure of the segfaults bit, feel free to put in your thoughts on that PR
Rust is a systems programming language that runs blazingly fast, guarantees memory safety and provides correct concurrency.
Rust is a systems programming language that provides uncompromised performance, convenience and security.
Rust is a systems programming language that enables unprecedented levels of performance, productivity and safety.
edit: I like (2) best