Swinging left just means simply that, getting LEFT after impact instead of
1) swing more towards "The target"
2) swing more towards "right field"
That's it.
Do you have to do this? No, of course not. Most players don't otherwise they wouldn't be hitting so many draws all the time. It would be mostly straight shots to slight cut shots.
The whole thing is if, IF, you want to hit it straight AND you have a negative AOA you must swing left ENOUGH to make the ball go straight. That's just physics. But again, you don't have too. I don't, because i play a slight draw.