Outside of not being able to prune or supercrop most autoflowering varieties, the stretch is essentially the same as with photo's. To increase stretch, for whatever reason you may desire taller plants, I guess you would avoid LST'ing and continually raise your light throughout the plant's stretch phase. Though I've not seen anyone actually desire taller plants, I suppose if you're limited on horizontal space and you have to choose between your plant growing upwards and outwards, I could see you opting for upward growth.