If fare rules applied in IROPS, I'd have failed to get home so many times I'd still be stranded in Atlanta. :P
For reference, here are the standard constructed routes for LAX-AUS:
MAP CONSTRUCTED LEFT TO RIGHT AND RIGHT TO LEFT
1. LAX-SLC/MSP/CVG-ATL-AUS
2. LAX-SLC/SEA/MSP/LAX/DTT/CVG/ATL-AUS
3. LAX-SLC/MSP-CVG-AUS
4. LAX-SLC-DTT-AUS
5. LAX-SLC-LAX-AUS
6. LAX-SLC-MSP-AUS
7. LAX-SEA/LAX-SLC-AUS
This applies even on a full fare F fare, so the agent must have been trying to break your trip into two separate fares.
Not that it should matter, but out of curiosity, were you traveling on a broken fare? And were you using an instrument (RUC/GUC)?