I think GFCI protection is not permitted because the article specifically calls for GFPE. From a practical perspective, a GFCI protected circuit would have nusiance tripping and would soon be replaced with only standard overload protection. GFPE is available in 30 or 50ma trip level and only in the breaker version. Cost of GFPE about $100 and cost of GFCI a fraction of that.
