This may be true, but reports also normally require a different schema from the OLTP database. Data warehousing with star schemas is a thing and it doesn't matter whether your OLTP database is an RDBMS or a NoSQL solution...you're going to have to push data to your warehouse to run those reports. The last thing you want to be doing is running reporting queries against a database that's required for the operation of your product, even if it is off hours. And reports will never run efficiently if they use a schema that's designed around the requirements of your business' application. For one thing, your update performance will tank since every write requires a ton of index writes. You can mitigate that a bit by maintaining separate indexes on a reporting slave, but that kind of maintenance has its own set of headaches.
So I'm not seeing how reporting is a good rationale for choosing one technology over another. Reporting, when done right, is a completely separate system with a completely distinct technology choice.