Go ask your mom why she never posts on her own website, but does on closed platform social media. Her answer will be the same as all the people outside of the tech bubble you're in.
I obviously don't know about that person's mom, but a lot of hosting platforms and blog providers will do that for you if you don't want to do it yourself.
> My tolerance for people posting to X without also posting to an open platform is over.
> Public institutions especially.
> There's zero excuse, none.
Maybe it wasn't their intent, but they clearly wrote it as a more general statement, with an additional and specific intolerance to public institutions, which is also how others interpreted it.