With Apigee X the role and permissions model has changed fundamentally.
Whilst the Apigee Edge permissions were based on paths of the management API, the Apigee X permissions are now based upon the GCP IAM permissions model of service.resource.action e.g. apigee.apiproducts.create.
A translation of Apigee Edge permissions to Apigee X permissions therefore requires a certain level of re-consideration that (currently) cannot be automated in a simple export - import script.