The form is operated through the conscious effort of channelling one's outward ki internally. Since that is optional, they can still use normal SSJB by simply choosing not to contain their auras. Take Goku's match with Jiren for example: when Goku charges at him, he still has bits of ki radiating around him like a regular SSJB, but they disappear soon after, signifying the activation of MSSJB.SIAD said:And there's the other interesting question, Goku and Vegeta getting the PSSJB, would automatically make the PSSJB replace the SSJB and make them become more powerful in their lower forms, so as not to have a very bestial gap between the forms PSSJB and SSJG ?