If you cut off a main branch now in flowering, the shock will be such that by the time the plant recovers, it'll be time to harvest.

Yes, the plant will divert energy into growth but it will be energy diverted to NEW FLOWER growth, NOT the flowers you already have.

Hence, the flowers you have will be already past their prime by the time the new ones show themselves and do anything worthwhile.

Use the veg stage to prepare the plant for flower. Once going into flower, you dont want to shock the plant.