Re:
Yes is my unxerstanding too. Bb30 bearing is 43 mm od and 30 mm id ( hence the name)
Shimano id is 26 mm, truvative 24/26 mm. I dont know what the od is but would be less than that for bb30 hence it will be a struggle to fit a bb30 bearing or adapter that is larger than the hole you are trying to fit it into.