Just a collective thought, this might apply to real life too.
Gwyn can’t go into a rage unless the opponent’s beyblade’s pattern and outcome veers off course either due to unnatural forces or sudden changes to the Beyblade.
Gwyn is always calm and collected within most of his battles and knows that he will win every time, which lets him perform extremely accurate and powerful launches which counter the opponent altogether.
However, when Dragon achieved ultimate awakening in the middle of the battle, the sudden change in performance confused Gwyn, veering his predicted outcome off course. This confusion in turn causes stress, aggression, resentment and ultimately the desire to win, even if it means destruction of the opponent’s Beyblade when he didn’t intend to destroy it yet. This can unlock some of the most powerful moves that Gwyn has never tapped into because he knows the minimum can win, and an Ignition’ driver travelling in reverse is just too much confusion as he might not ever be able to calculate how and when Dragon will veer backwards.
Let’s say in this state, Gwyn will force Genesis to switch play styles from the minimum to the maximum, braking his own sanity in the process as he veers further away from a calculated success. This can make Genesis make erratic movements and switch from standard Defense and Attack states to a crazed performing attack state, using everything he can even if it means just to win.
You can say that even Ryuga (Metal Fusion generation) can be a formidable opponent due to Lightning L-Drago supernaturally switching from triple-attack mode to smash attack mode. (If he used a weaker bey)