Microsoft launches unfinished Windows builds (software). Apple launches unfinished Lion builds (software).
The question is flawed in that it assumes that they companies have different release methodologies for the same class of products. Both Microsoft & Apple are making similar choices for similar classes of products.
What Gruber is doing is comparing release methodologies of different classes of products that are in the same market space. What drives the choice of release method is not the market space, but the nature of the product being released.