French Guyana has lots of forest :) but I think you're right, the article ratio is for France métropolitaine indeed.
As usual wikipedia has more, 166e3 km2 of forest (30% of 550e3). Interestingly:
Les peupleraies qui occupent environ 30 000 km² ne sont pas considérées comme des forêts, et sont incluses dans la surface agricole.
So that makes 166+30 = 196 = 35.6% of surface.
Lots of the total is privately owned (~ 70%), but it looks like use and planning is controlled.
French Guyana has 77e3 km2 of primeval forest.
I let Jerome comment on wether it's significant or not in the big picture :).
