In fairness, this is just doing something automatically that you could have done manually anyway. It's a good change because defaults matter, but it's always been possible to strip debug symbols from Rustc-generated binaries, and all the guides I've seen to reducing binary stuff have mentioned this already.
It's also important to remember that in embedded software, you're probably working in a no_std environment anyway, which means that the Rust standard library doesn't need to be included in the binary, which will already significantly reduce the size of your binary.
A lot of this is about tradeoffs, and I think the article does a good job of explaining what tradeoffs are relevant here. Yes, binaries should be as small as possible, but shipping multiple compiled standard libraries is also not ideal. The Rust team seem to have gone for a good default for people who are beginning, with lots of ways to tailor the build process for people who don't need debugging information, or who are willing to accept longer install/compile times in exchange for smaller, more optimised binaries.