It very much is. If you told them you might decide not to use mysql so it would be completely incompatible with all of the data storage requirements, they would rightly tell you to get out for wasting their time. Your refusal to use the correct storage could cost them thousands of hours of labor establishing new processes for backups, BI integration, high availability, and just training on managing the system.

I have worked with many companies where this was a very hard business requirement. Companies that dont care how the data is stored tend to be pretty small or not actually care that much about the data.