FCC is teaching the version of React that was active when the curriculum was being developed. And these techniques will continue to work for people who are using the older versions of those packages. Many libraries have deprecated features that work with older versions but not with the newer ones - this is a fact of life in web dev where all these packages are developing independently and sometimes have breaking changes, sometimes changes that break other libraries. Sometimes you have to find the right combination of versions. Without a crystal ball, it is impossible to predict for sure what React will look like in a few years.
But if you think it is a big enough issue, you can raise it on github. I see that there is an old post about someone mentioning that in the code issues, but I don’t see anyone that has brought it up in the curriculum.