There are endless arguments over all this. I am now at the point of ignoring the question. It suffices to state that I personally presoak everything briefly, whether film or paper. This not only helps the developer spread quickly and evenly, but pre-tempers the material to the correct working temp itself. This is very important
with drum processing in particular, to get the inside of the drum itself to the correct temp. With sheet film tray processing, you want the emulsion to swell prior to putting it in the developer. pr the sheets might stick together at exactly the worst time. It's just a settled question for me.