For maybe 20 or 30 years I didn't presoak, and in fact had never heard of it. This for 35mm and 4x5 in an inversion tank. My agitation was vigorous for the first minute after a couple of sharp raps on the bench to dislodge airbells which I have not experienced since the 1960s. Then remaining agitation every minute thereafter. I gradually moved over the years to less frequent agitation after the first minute to control contrast.

When I started to use 120 size (Neopan 400) I had a few random little circles of slightly reduced density, visible in prints in clear sky only (maybe 0.5mm diameter leading to a few mm on an 8x10 print). I became very particular about rapping the airbells and agitating fairly vigorously but I still got them. I started to use presoak, 2 min fairly vigorously, followed by dev as usual. The problem went away. I still don't have a good explanation, but it works for me.