I maintain that having a multiple of identical components in a system that perform the same duty is horizontal scaling. There are many reasons to scale horizontally, and I'd say increasing capacity is exactly what Aero would be interested in, not to mention fault tolerance. My career is based on building distributed fault tolerant systems, which is potentially why I think I understand their approach differently than you do.

But yes, horizontally scaling systems comes at a cost, sometimes they are more inefficient, sometimes they cost more, but in the long run if it helps you meet the goals of the business it shouldn't be illegal.