That's interesting -- sounds a bit different though. This is more like an overall stain than streaks. But using a stop probably won't hurt at all. I'll make up a 1.5% or so acetic acid.
I believe the benefit of pre-soaking to be largely about pre-equilibrating the temperature. If you apply the warm developer solution over a large, cool area, you'll get a big and sudden temperature drop, so your careful temperature control is wasted.
But there may be other explanations, and I have no 'attachment' to any aspect of the process.
Pretty soon I'll have my Durst RCP-20 re-geared for RA-4 speeds, which will hopefully improve consistency at least (and be less schleppy)