Harry, I don't have first hand informations on how hard is, but by reading here and there I learned that it requires more attention. Now usually, graphite necks come with a phenolic fretboard which is stiffer than wood and more indicated to be happily 'married' with the graphite. There were cases where the wooden fretboards, very rarely used, decided to 'divorce' (just to stay in theme) due to normal temperature/humidity changes.
In the case of this one in the link there is a wooden fretboard, so I assume it would be like a refret on a any other fretboard, unless I'm missing something.