Yup. And I like the implication that Rust is 'cross platform', when it's 'tier 1' support consists of 2 architectures (x86 & arm64). I guess we're converging on a world where those 2 + riscv are all that matter to most people, but it's not yet a world where they are all that matter to all people.
[1] https://doc.rust-lang.org/beta/rustc/platform-support.html
The converging is happening in practice. I’m using a keyboard running RMK for firmware, written in Rust.
You are misunderstanding what Tiers are. Embedded architectures cannot be Tier 1 which requires running Rust compiler compiled on the architecture itself and testing stuff on with it. Only full desktop systems will be Tier 1, because those are the systems that you can run Rustc and all the nice desktop environments.
However most of the embedded world uses ARM chips and they are Tier 2 like thumbv6m and thumbv7em (there are still odd ones like 8051 or AVR or m68k, many of them lack a good C++ compiler already). They are guaranteed to be built and at the release time the tests still run for them.