I was specifically replying to the "especially" bit. The net benefit of an SSD is far less pronounced with many NoSQL solutions (in particular document stores)

I was specifically replying to the "especially" bit. The net benefit of an SSD is far less pronounced with many NoSQL solutions (in particular document stores) than with relational databases. That's because the former was built and adopted largely to make lemonade out of the I/O problem (particularly on terrible I/O platforms like AWS).