Rabbit Hole is a workout that strings along a series of related exercises that load the body's back and front kinetic chains, task the four abdominal muscle groups and recruit satellite muscles to ensure optimal stability.
@Kiceres I think both @HellYeah and @kandy have answered your question here. What I will add is a little extra knowledge. We can exercise muscles in either an isotonic or isometric ways. Isotonic refer to exercises that make muscles contract and relax (the 'pump' you mention here). Isometric exercises are contractions of a specific muscle or group of muscles. During isometric exercises, the muscle doesn't noticeably change length. The affected joint also doesn't move. But the muscle still gets to work. In general terms isotonic exercises help build strength while isometric ones help maintain it.
In the Rabbit Hole workout there are several exercises where leg muscles are asked to perform both isometric and isotonic work in succession. The perceived load they experience then is key to creating the pressure required for adaptations to take place. I hope this helps add greater clarity to the workout.