Actually, no, they were building their own boxes.
Even if they were building their own sheet metal lockers, I still don't think they were a "hardware" company. They had a great service and that's what they were selling.
Bufferbox offered a service and didn't sell you a product therefore I don't think they were "hardware" company. The hardware was means to an end.
I don't think it lessens what they did. It was a good service.
Walmart has a large IT infrastructure, with sys admins and in-house developers. They also manage a lot of buildings, and warehouses. I wouldn't consider them an IT company, a property management company, or a logistics company.
I agree with your points regarding BufferBox, but I wouldn't say they are a hardware company producing a hardware product that you can sell to a customer. They were in an entirely different space, with very different set of challenges.
The YC post concerned companies that sell hardware to end users. Further, the initial post in this chain was someone asking if YC has had other hardware companies beyond Pebble. I don't think BufferBox is in that category.
Your manufacturing pipeline, volumes, service issues are all very different. So as great as BufferBox was I don't think they were a hardware company and certainly not for the purposes of this thread. I am not discounting their abilities or what they made but based on my experience they are apples and oranges.
Most of the problems kickstarter companies run into are unique supply chain, and manufacturing issues that BufferBox wouldn't have had to deal with.
Additionally, a big part of what BufferBox offered would have been in their app, and website. A locker that you can remotely lock and unlock is not difficult from an electronics point of view and had been around before.