Revit is only certified for linking IFC4 as a reference. Opening IFC4 versions is so badly supported by Revit, that basically you lose half of your model in some cases. This is the reason we cannot add IFC4 support in our AddIn, since we only improve the imported model, not do the import process ourselves.
As for the export: we thought to keep the I/O possibilities in sync, but since there is an increasing amount of requests about it, we are planning to add IFC4 export option to our addin as well, in an upcoming update or at latest for the Revit 2025 version.
I'd love to hear your feedback on which workflow are you most interested in? Importing to Revit or Exporting from it?