The five-nines was a commonly used marketing claim used by companies about the product/service/system they were selling, it wasn't and isn't being applied to a

The five-nines was a commonly used marketing claim used by companies about the product/service/system they were selling, it wasn't and isn't being applied to a general context. I think the point being made there is not that all the computers/software used to be better/perfect but that the fact that such claims were used and became so prevalent shows that reliability was a feature and even an expectation.