While that might be a valid reason to require MySQL as a database, it's probably not a requirement of a given form. It might not even be necessary to have a database at all - it's important to understand 'why' the BAs are saying this, and not take their opinions as the definitive solution.

For example, the ticket might look like "When I submit the form, then the DB Analysts are able to run reports on the submitted data".

The decision about what database to use still isn't a business requirement in that case though, more of a nonfunctional requirement that can be determined outside of a particular feature.

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.