They don't choose not to sell any model as manual-only because the auto can't handle the power. If anything, it's the other way around.

A manual that is setup for the I4 variant of a model won't necessarily hold up to the torque of the V6 variant. The same goes for the automatics, but it ends up being cheaper to make the necessary "tweaks" to the auto than the manual. At least when they expect more people to purchase the auto version of that trim level/engine configuration anyway.