I would not call myself an operations expert by any means, but I have done quite a bit of infrastructure work in the past; both with bare metal setups and cloud based solutions.
With that said, the old database specialist position was about 80% engineering, 20% infrastructure, with the infrastructure work being done in cooperation with the production engineers.
I left the database team a good year ago and quite a lot has changed since then. I think these days we have a handful of people focusing on the database side of things.
To be fair it depends a bit on the context. I present myself sometimes as a database expert and other times a Ruby/C Developer. And I would argue that I, as a minor PostgreSQL contributor who follows the mailing lists, am more knowledgeable than most about databases and especially PostgreSQL.
Edit: Admittedly while I have done a lot of DBA stuff and server operations on top of my software development, hardware and networking are not my strong points so if the company could afford it I would want a more traditional server/networking guy on my team (and at a previous job I did exactly that). And I agree their job posting seem to have a very heavy focus on development experience.
Obviously this doesn't preclude operations or systems knowledge but again, it's at least telling of the mindset.