Equatorial Guinea is marked on that map as a member of CEMAC, not as an ex-colony of France. Although yes, the short text does imply that they’re all French ex-colonies, while Equatorial Guinea is actually ex-Spanish.
Equatorial Guinea is the odd country out in the CFA currency zone; the other five countries were there when the treaty was established in 1966, whereas Equatorial Guinea adopted the currency in 1983.