Not even the most extreme FOSS zealots (RMS, FSF, …) ever claimed that taking public contributions was ever a part of that.
But that's a bit backwards. RMS would emphatically agree that Free Software doesn't mean being open to contributions; if you asked him about either "FOSS" or "Open Source" he'd probably command you to wash your mouth out with soap. It's the other side of the fighting FOSS family which evangelised for Linux-like development (see the thread from https://news.ycombinator.com/item?id=48410503 ).