I'm no longer with CA so you may want to follow-up internally for certainty.
We can presume that since these values are immutable once used for financials, and that the IDs are unique, it could help avoid mis-entry against the wrong item as it should be made clear which values are to be used and which are not with values that remain consistent and distinct.
Should that mean the descriptive name couldn't have been included in the display too? No, there appears to be adequate UI space for it nowadays**, but that is not the way things are and it would take development time (however small) to be committed to change it.
** Back in SVGA times the same number of columns were on a timesheet and the real estate to fit them was more scarce. Timesheet appearances haven't actually changed that much since then.