The description itself would not be stored in HRP1002 when you display the posn in SE16 for HRP1002. The HRP1002 record provides a link to another table (I am not sure which one; you'd be able to see the table name in the prog module for PO13 txn).
The same applies to PA infotypes - text info.
Further when you create text infotype, the default start date for the PD infotypes is current date, which can be changed when creating.
If you want to change the eff.date, then copy the row to another period; when the two records are consecutive, the records are combined, when you go back to display. This behaviour is observed in PD infotypes.