Thanks for that but I guess I should have been more specific.
I know about the non-stop LAX-LHR flight and in fact took it the last time I did this route back in October. However, AA 136 arrives at 12:25 pm, missing the 11:00AM BA flight to BOM. You then have to wait for the 9:30PM flight. By taking the BA flight, one can arrive at 09:30 and make the earlier flight, saving a bunch of time.
Main issue is that the flight would be for my dad, not an AA Plat member like me, so for him, he'd rather have the shorter journey. I was just wondering if there was anything to be aware of (other than no miles!) in the combination of award + paid travel. Sorry for the confusion.