Yes it is a good idea, training one muscle a day is pretty much OLAD with other accessory lifts, example of what you would want:
1 back - DEADLIFT + pull ups? db row? seated row?
2 chest - BENCH PRESS + incline bench, pec deck, db press
3 bicep - BARBELL CURL + preacher curls etc.
4 shoulder - MILITARY PRESS + lateral raises, rear delt raises, db shoulder press etc.
5 leg - SQUATS + leg curls, lunges, leg presses
6 tricep - WEIGHTED DIPS + cable press downs, db extension
I don't know why people would recommend OLAD and wouldn't recommend 'focusing on one muscle group a day', it's the same thing! Except with adding more exercises; it would be be more focused to developing balance between muscles (bodybuilding).
I gained a lot of mass by doing the routine above, made very good gains on the main lifts and didn't have any lagging muscle groups.
I would only recommend a program like this for someone trying to gain mass though.