Give us an example. What standby workloads are you seeing?
The AWR Report reads what has been written by MMON process.
What has been written by MMON comes over in the Redo threads from the Primary
to the Standby. MMON itself on the Standby does not and cannot be update the Repository.
You cannot generate an AWR for the Standby because the data itself isn't written.
You cannot run AWR reports in a physical standby database because there are no snapshots to base the report on. A physical standby is in managed recovery mode and/or read only. It is not read/write so AWR snapshots cannot be taken.