The R5 3600 is a 65W processor which is stable with the OEM cooler provided. Shipping from China has been slowed due to the coronavirus debacle.
The larger Wraith Prism cooler uses the AM3 type bracket which makes it easier to swap the processor. The studio is adopting this larger cooler primarily so that it is faster to test motherboards as the cooler clips on quickly.
Excessive handling of the motherboard is more risky. With the OEM cooler, the motherboard has to be removed. The Wraith Prism does not require that. Complicating the OEM cooler is the need to secure the backplate so that the unit is secured with the cooler tension screws.
With a pair of processors there is a need for at least 2 of the Wraith Prism coolers which should be cooler in operation as the studio prefers to use 65W processors or lower.
Some games tend to push the CPU hard which is thermally stable with the OEM cooler. The larger Wraith Stealth cooler simply allows more thermal capacity.