Users reported rendering speeds up to 2x to 4x faster , depending on their system's core count and RAM.
This tool was added to help users identify which specific layers and effects were consuming the most processing time. HUGE After Effects News - Multi-frame Rendering
The 2021 updates to After Effects (primarily and v22.0 ) focused on a major architectural overhaul to modernize performance through multi-core processing and enhanced 3D design workflows. Core Performance: Multi-Frame Rendering (MFR)