Auth obj missing for SAP delivered tcodes in SU24

Hi experts,

We are maintaining auth obj for all tcodes in SU24. We have turned on some auth objects that were not proposed (PROPOSAL -NO) by SAP by default. But there are some objects that are missing in SU24 for some SAP delivered tcodes.

For ex. We have ME21n( create PO) which is checking for F_FMMD_MES. this is based on the trace results (ST01).

But when we check in SU24, it has several other FM auth object but this particular object is missing.

Can we add this object in SU24 and maintain it?

Is it a good practice to add auth object in SU24 for SAP delivered tcodes?

Please let me know

Thanks

Kee