Hi bud . No topping is not necessary before LST . Infact as you are growing an auto I wouldnt top at all. I find it's best to LST as this means you can shorten the plant and get all the tops to an even level . Pretty much spreading the plant out instead of allowing it to grow tall. Giving you optimal light coverage Increasing yields. But each to their own, some People choose to just leave autos alone completely as they can stay short anyway .
I'll be uploading a few pics this week of how I LST in the next few days 👍