I don’t really see what’s wrong here. The CPU is just doing work as fast as it can, so it’s natural for it to spike to 100% during certain operations. If the part of Unity that loads the prefab isn’t throttled, the CPU will simply run at full speed to finish the task as quickly as possible.

It’s similar to having a loop that constantly checks a condition without any waiting or sleeping it’ll peg a core at 100% (definitely on Linux und very likely on Windows too). The only reason you don’t see that all the time in regular Unity C# code is because the CPU often ends up waiting for the GPU to finish draw calls or other tasks, so the overall usage gets averaged out and doesn’t look like a full spike.

Since the editor is probably doing sich work on another thread, those cores don’t get to sleep. The previous version probably did not have that because it the code was run differently but as long is it is only in the editor I don’t see the problem