That takes some level of hypocrisy - you are not making your Atlas as opensource, but you require others to do so.
This clearly indicates that you are using an opensource license as an extortion schema against competitors.
It absolutely does not make them hypocritical. They own the copyright and can do as they choose. They simply don't want other companies getting rich on their back by simply offering a MongoDB SaaS. Why is it OK for AWS to just take a project and start making millions off of it while the people who invested in the project get nothing? AWS and similar cloud companies are simply trying to strip mine all the value from some popular open source projects and contribute nothing back. Most of these cloud companies show zero interest in partnering with the copyright owners so now we're seeing copyright owners take a stand against this exploitation.
There's a big difference between a piece of free software being vital to your codebase and you simply selling that free software as-a-service.