I'm bumpin' this in order to add related information.
As you can read HERE there's a side discussion about true Stone's effect. On Class Reforms & Action Lists you can read the following regarding Stone spell:

CNJ Mag. 10 Deals earth damage to the target. Chance to reduce evasion against earth magic.
Gael from Rabanastre World stated that this is the case for Stone spell's description on French client, but on English client we get different information as Zetsumei_Tsunarashi described above. The exact text is the following:

Deals earth damage. Chance to inflict Evasion Down.

I would like to read an official response in order to clarify this matter. Thanks in advance!