Ultimatums reduces overfilled adrenaline. Nearly every time the adrenaline bar is filled to 100%, 1% to 7% or 1% to 12% (with Invigorating 3 and Impatient 3) depending on adrenaline boosting perks and effects, is wasted. For example, using Wrack with Invigorating 3 and having Impatient 3 activate generates 13% adrenaline. If used at 99% adrenaline, the adrenaline bar is filled to 100%, but the remaining 12% adrenaline is lost because the adrenaline bar cannot exceed 100%.
This much adrenaline lost every time a player reaches a full bar can be 3 to 6% DPS lost, which is what usually lessens or negates most adrenaline saving effects. This makes any adrenaline boosting effect pair greatly with Ultimatums, as if a player correctly times their use of Overpower, Frenzy, Unload, Omnipower, and thresholds, they can fully recover all overfill adrenaline on top of saving 15% adrenaline if they only use the ultimate abilities affected by Ultimatums.