Board Thread:Fun and Games/@comment-27996636-20171206104646/@comment-27996636-20180106102209

I think the spirit bomb more fueled him for the fight rather than acutually gave him the UI power, he was all out of energy for fighting and needed an energy source to use to continue. It helped trigger it with the damage and helped him continue the fight with energy, but was not the reason Goku turned UI, as we saw with his battle against Kefla.