You presoak film to dissolve the anti-halation backing, and to bring the tank and reel to working temperature. It would be totally pointless to bust your tail to get your developer temperature on the money, and then pour it in to a cold taknk, or a hot one. So you presoak with water of the same temperature as the developer is going to be.
Yes, Fomapan 400 in 120 can throw green vomit after two minutes of presoak @ 20°C.
OM-1n: Do I need to own a Leica?
Rolleicord Va: Humble.
Holga 120GFN: Amazingly simple yet it produces outstanding negatives to print.