Why is SF4 hydrolyzed in water whereas SF6 does not?

SF4 is having sulfur as central atom is dsp3 hybridized forming a see-saw geometry

 Due to presence of lone pair of electrons on the sulfur atom the axial bonds are repelled due to Lone pair bonded pair repulsion. Thus there is a dipole moment on the molecule which is away from lone pair of sulfur.
Due to presence of dipole moment the molecule when reacted with water gets hydrolyzed. As after hydrolysis the dipole moment gets nullified at equatorial atoms
But in SF6 the central atom S is d2sp3 hybridized having octahedral or square planer geometry.The structure of molecule is

In octahedral geometry the over all dipole moment is Zero and stability of molecule is high thus when SF6 is reacted with water it does not get easily hydrolyzed.