It seems to me that there is a 1:1 correlation between mass of virtual particle and field stiffness. Given that fact, why isn't it equally correct to say "The field stiffness is caused by the mass of the virtual particle" and "The virtual particle necessarily has mas because the field is stiff"

The author states that "it is short range because the particles that “mediate” the force, the W and Z bosons, have mass;" is misleading as to causality, but I missed the part where they showed how/why it was misleading.