meaning that once upgraded the policies should work as expected on the new version of the system.
a 10.x policy containing Keyword and Data Identifier rules will not work on import to a version 11.x system because of enhancements to these rules for version 11.
Consider a situation where you are evaluating a new version for potential upgrade. In this case you install a version 11.x system and to that system you import your
10.x policies to verify the potential upgrade. Here you would need to rebuild the imported Keyword and Data Identifier rules on the 11.x target system.
However, when you actually upgrade from 10.x to 11.x, the policies would upgrade automatically without the need for manual intervention.
Above description was reflected on v11 latest upgrade guides.