My main reason for pre-soaking is temperature balancing of the development tank and film.(posted 8433 days ago)I have several times noted that if I pour in 20°C water in the tank, agitate the tank and measure the temperature it might have changed to 18.5 or 21.5 degrees, although the ambient temperature is kept between 17 and 24 degrees. This will of course influence the development if no pre-soak is used.
I am using plastic Paterson tanks, and always pre-soak to get the tank and film adjusted to 20°C.