By the time the transient reaches the voltage regulators, it's old news. We're talking about a base clock in the multiple GHz, which means the edges of power st

By the time the transient reaches the voltage regulators, it's old news. We're talking about a base clock in the multiple GHz, which means the edges of power steps have harmonics in the tens of GHz, which means wavelengths on the order of millimeters. When they talk about package and board inductance, think of it as meaning that the board itself is a transmission line and its characteristic impedance is limiting the risetime of the current waveform. No amount of regulator response can overcome that.