Having the coordinates and version in the version catalog is perfectly fine, you just then have to use it in a constraint. So yes, defining the versions centrally in a version catalog is fine, but as Chris said, the version catalog is just as the name suggests a catalog with coordinates and versions to pick from. But just having them in there does not yet have an effect without using them somewhere. Using them in a platform that you then use in the projects is perfectly fine. When the question is whether to use version catalog or platform, the answer is often to use both. 🙂