This triggers a memory of something in "Naturalisic Photography" by P.H. Emerson.
The focus was changed during exposure.
Then there was the grain suppressing technique of diffusion induction over several exposures with the enlarger by Merlyn Severn. You used a variable diffuser under the enlarging lens. Your main 2/3 exposure was for sharpness. The remaining 1/3 was divided between half diffusion and full diffusion.