The title in the article is literally "Async Rust vs RTOS showdown!" and the article shows "Embassy/Rust against FreeRTOS/C". There should also be a (2022) appended.
You just need to read the Reddit comments to see why this is not a useful comparison [1] [2].
Technically RTOS’s can also be cooperatively multithreaded, to some degree at least (see FreeRTOS). The comparison is valid IMO as threading with fixed yield points is an abstraction that isn’t exclusive to async Rust.
Perhaps "Embedded async Rust vs. C RTOS"