Technically they do via a footnote... but it's a pretty confusing one at that!
The FLS stood for the "Ferrocene Language Specification". The minimal fork of Rust that Ferrous Systems qualifies and ships to their customers is called "Ferrocene", hence the name. We'll be dropping the expansion and just calling it the FLS within the Project.
So now it stands for... nothing. Bizarre.
This has to be a joke.