This is correct! By default, Pd uses a “polling scheduler”, which means that the scheduler runs in a dedicated thread and communicates with the actual audio callback via a lockfree ringbuffer. This means the audio callback does almost no work. The size of the ringbuffer (= “delay” in Pd’s audio settings) introduces additional latency to compensate for CPU spikes and non-RT-safe operations. This is necessary because Pd runs DSP and control code deterministically in the same thread.