Yes, maybe it should say “This is an old feature of React that they recommend is not used for new code that you write. The reasons are mentioned here (link to docs…). We include this lesson so that you know how this works when you see code other people have written using componentWillMount in their projects.”
I’m not so great at phrasing these things but hopefully that’s the gist!
I would consider most of the React curriculum legacy at this point. Not saying you shouldn’t know about it, just that it isn’t exactly the most up-to-date course on React.
I do not think skipping it could be a good idea but somehow finding article about async rendering that is dated after 2018 is really hard
What happened after 2018??