It's not an experience for professional typescript development, but the experience that professional typescript developers are used to.
This isn't in competition with C or C++, it's in competition with micropython. Python isn't a great language except in its ubiquity. I'd rather work in what I know, which is TS. This opens up microcontroller development to JavaScript devs of whom there are a lot of us.
Types are really helpful when dealing with unfamiliar APIs. When doing embedded projects, you deal with a lot of APIs. There are the language built ins, any libraries you are using to interface with peripherals. This project opens up microcontroller development in a big way to a LOT of developers.
Is it what you want to use for a commercial embedded device? I can't say. Is that the only standard? Then you should just be using C for everything, I guess. But something like a Raspberry Pi Pico or ESP32 has plenty of resources to run JavaScript while still being able to manage a weather station or automated garden or security camera or pen plotter. There are lots of applications that don't use the full power of the board.
If you tell me is a toy, and somebody's pet project: fine. Is all about having fun.
But then don't mention "professional" in the project description.