Previously Goku had to revert to base form to use the spirit bomb due to the natural rage and volatile other emotional spikes. SSB however has a calm mind such that it enables him to use SSBKK, could the same principal be applied to the Spirit Bomb?
I know that but did he NEED to? I’m also wondering if the anime writers may have just forgotten the reasonings for certain things, such as Trunks going buff when he shouldn’t be able to do that after obtaining MSS followed by SS2. I guess you could say it’s just me theorizing.