>Designers design for usability.

It wasn't usable for the majority of the market. Even in the infamous mea culpa Apple made about it, they admitted they designed themselves into a corner. It was designed so poorly, they had to take years to undo it after admitting it needed to be done.

Right, but that doesn't change the fact that usability is part of design, not something separable from it.

GP was complaining about the common and incorrect trope that design is limited to aesthetics.

I think he was complaining that Apple was the one that had lost the plot and had started separating the two, not that they should be.

I think it's pretty much impossible to determine apple's intent here, for the obvious reasons.