2/3

Right: in neo-Darwinism, variation merely supplies raw materials and has no dispositional role

Wrong: this is not based on assuming isotropic variation

Instead, Darwin and his followers argue explicitly that selection governs evo, so that the details of variation don't matter

They argued this in many ways

That's the real problem. Today we know today that biases in the introduction of variation can be dispositional causes in evo. This is well established theoretically and empirically