This is somewhat inaccurate and requires clarification.
The first, potentiating, means is not restricted to being a “very slow, heavy movement, like a near max lift”. All that is required is that the first means present a greater overload than the second relative to the biodynamic character of the second means.
A tonic means, such as a slow heavy movement (ergo barbell squat), would be used to potentiate a more explosive movement; either still with overload such as a jump squat, or without, such as an unloaded jump
A phasic means, such as a jump squat, may also be used as a potentiation means for a subsquent unloaded speed strength means.
Second point of correction is the rest interval. The bioenergetic/biodynamic character of the potentiating means, in either example, is one which demands heavily from the ATP/CP reserves and the subsequent explosive/speed strength means rely heavily upon these same biochemical fuel sources in order that they be executed with max power.
Thus the rest interval between the last set of the potentiating means must, on average, be 5-7 minutes prior to the performance of the explosive/speed strength means in order that complete regeneration of the biochemical fuel source occurs; thereby, allowing the subsequent training means to be exploited to the fullest in terms of maximal results.