Sable hair is good for watercolour because of it's water holding capable. However in a brush pen like this, it's actually holding ink, and secondly there's always the ink flow from the cartridge so it doesn't really need the holding capacity -- the ink flow just has to be good.
The difference is not significant.
Sable hair is good for watercolour because of it's water holding capable. However in a brush pen like this, it's actually holding ink, and secondly there's always the ink flow from the cartridge so it doesn't really need the holding capacity -- the ink flow just has to be good.