This documentation is essentially misleading.  This variable does naturally not reflect the standards which are *currently* installed, but rather those standards that were installed *by the time Flycheck was loaded*.  This variable does not pick up any standards that were installed *after* Flycheck was loaded.

That can be a significant differences, given that many people tend to leave their Emacs session running for days or weeks.  If you install a 3rd party standard after loading Flycheck, it won't be contained in this variable.

So I don't really see the point in this.