Just because it claims to be compatible, it does not mean it really works in practice. If you try to perform a ReqIF-based data exchange between two different tools, it will probably not succeed at the first try. Why?
Most requirements tools do not support all ReqIF features! ReqIF is a very rich data format, and not all tools support all features. In fact, ReqIF capabilities are often added "after the fact". In the worst case scenario, only a ReqIF-exchange to the same tool will succeed.
This article will provide you with guidelines for configuring your requirements tools and the data exchange, in order to minimize problems.