tlkn,
It's our pleasure to help out!
It sounds like you did some digging into this concern on your end as well, which is great. I just wanted to reply to share some additional information that will help clarify things a bit more with iMessage and FaceTime on Mac.
Take a look over this page from the FaceTime User Guide as well: FaceTime requirements on Mac - Apple Support. This article goes more into detail about what is needed in order for FaceTime to work on Mac. This includes iMessage too, since they are both Apple ID services. iMessage and FaceTime services on Mac, work through Continuity. In other words, Continuity is what connects your iMessage and FaceTime services from your iPhone to your Mac, and any other devices: Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch - Apple Support.
We hope this adds further clarification. Thank you for using the Apple Support Communities. Take care!