> which can result in behavioral bugs in safe Rust
For example, Rust doesn't have any way to know that your chosen lock-free algorithm relies on Acquire-release semantics to perform as intended, and so if you write safe Rust to implement it with Relaxed ordering, it will compile, and run, and on x86-64 it will even work just fine because the cheap behaviour on x86-64 has Acquire-release semantics anyway. But on ARM your program doesn't work because ARM really does have a Relaxed mode and without Acquire-release what you've got is not the clever lock-free algorithm you intended after all.
However, if you don't even understand what Ordering is, and just try to implement the naive algorithm in Rust without Atomic operations that take an Ordering, Rust won't compile your program at all because it could race. So this way you are at least confronted with the fact that it's time to learn about Ordering if you want to implement this algorithm and if you pick Relaxed you can keep the resulting (safe) mess you made.
For example, Rust doesn't have any way to know that your chosen lock-free algorithm relies on Acquire-release semantics to perform as intended, and so if you write safe Rust to implement it with Relaxed ordering, it will compile, and run, and on x86-64 it will even work just fine because the cheap behaviour on x86-64 has Acquire-release semantics anyway. But on ARM your program doesn't work because ARM really does have a Relaxed mode and without Acquire-release what you've got is not the clever lock-free algorithm you intended after all.
However, if you don't even understand what Ordering is, and just try to implement the naive algorithm in Rust without Atomic operations that take an Ordering, Rust won't compile your program at all because it could race. So this way you are at least confronted with the fact that it's time to learn about Ordering if you want to implement this algorithm and if you pick Relaxed you can keep the resulting (safe) mess you made.