Newer AMD CPUs are designed in a way so that the CPU's hotspot is located towards the bottom (south-side) of the processor. This is due to AMD's chiplet design: The cores (CCDs) and I/O die are separated on the CPU. While the I/O die is located in the middle of the CPU, the CCDs (either one or two depending on the specific CPU model) are positioned below the I/O die.
As the most heat is generated by the CPU cores on the CCD, this area of the CPU becomes the hottest and needs the most cooling.
This is where you can use the offset mounting kit, as it shifts the cooler's highest pressure point directly above the chiplets. This ensures the highest efficiency in thermal transfer at the most crucial position.
What can I expect in terms of performance?
Giving a performance estimation is difficult as it depends on several different factors. A difference between 1 and 3°C is realistic on Ryzen 7000 series CPUs. However, for Ryzen 5000 Series CPUs, the gains are much lower. These gains can be used to let the CPU run cooler, to achieve higher boost clock frequencies or to reduce fan speeds and noise levels.