Continuous load is not the use case the beefy cores on phones are designed for. They exist for bursty loads related to user interactions. Humans are fairly slow, but each touch can generate a substantial workload. Being able to handle that workload quickly and then sitting idle is what these cores do. Continuous load runs on the smallest cpus possible or ideally offloaded entirely from the CPU to others subsystems. The goal here is to minimize power usage while maintaining good user experience.