Jobo started recommending the presoak when they discovered that using it allowed customers to use published times for small tank inversion development. They confirmed this with multiple films and developers. When Kodak developed (pun not intended) Xtol they tested and published time for continuous agitation that did not include the presoak. I've done TMax with Xtol in the Jobo with and without the presoak, once the process is calibrated I could see no difference. I decided years ago to stick with the presoak.