During my casual playthrough, I skipped the 2nd phase of Kang-Jin Star by hitting her with a t4 smash attack. At the same time, she was immobilized with the damage up upgrade on immobilize, I did a ton of damage, but then she never transitioned into a 2nd phase, I'm not sure if this could be possible on other bosses, or if it would save time, but it could be something.

Was this a one-time occurrence, or have you been able to replicate it with other Block Blast bosses? If it was a fluke, it might not be a reliable tactic. However, if you can consistently trigger this behavior, it could be a valuable strategy.