Gradually switching production of 3 from those 6 factories to produce Spits makes more sense IMO, than all of the 6 further producing Hurricanes.
Read my post above regarding the practicalities of keeping the Hurricane in production, not only that, but to tool up and produce a different structure altogether (the Spit was a semi monocoque and the Hurri was welded steel tube) was not something that was going to happen overnight. The Hurricane was still a useful type throughout much of the war, why not keep producing it?
Besides, politics played a part in these things too, private firms were striving for contracts; Hawkers and Vickers Supermarines were competitors in the same market. One's companies were not going to produce the other's machine; not without considerable justification and pressure from the ministry.