Well the answer to the question is that it depends on the bloom booster. If it is a solution that offers a high PK then it is a fertiliser and it's use as a booster is questionable. It is a supplement that offers more food and forces the plant towards a certain growth direction, most of the time unsuccessfully because of nutrient burn, although most people don't have the honesty to admit this mistake. These products are for use straight in the ground not for containers and it is the plants' own strength that hides their failure most of the time... For those that use chemical fertilisers they are the only solution they have.
Another category are a different kind of activators/boosters that might contain a low NPK value but they stimulate growth by offering aminoacids, vitamins, micronutrients, increase microbial life in the medium etc. These are not really fertilisers but in autos or in the blooming phase of photos do promote flowering, because they increase the overall health of the plant and the medium and help the plant absorb it's food from the medium. They can be used through vegging as well to promote growth. You can either make them in the form of teas or purchase ready ones. But they require an organic feeding schedule to work.
It all comes to you to decide. If you want a lot of weight and no quality or a slightly lower or equal weight and quality. This will determine the main fertiliser and therefore the kind of booster you will choose.
Experiments in the middle of the way, for example organic base with heavy chemical amendments for boosting tend to fail because of nutrient burn. The other way around with chemical base and organic boosters fail because chemical fertilisers kill microbial life in the medium so the booster has nothing to work with.