I have used the Redline 75-90NS for the last 35+ thousand miles. It never made the going into 1st gear issue any better. But the cold shifting was easier. I just changed to Redline lightweight Shockproof and it feels a tad smoother in all gears. But the 1st gear issue has not changed.
My friends 2002 WRX shifts just fine in every gear and he just changed to Redlines 75-90 weight GL5 gear oil from the stock fluid. He says it shifts just like before and he has never had the difficult getting into 1st gear issue ever.
It just goes to show that some trannies work well and some don't. Why? I don't know. Manufacturing tolerances? Bad batch of syncros? I have read that even some of the 03-04 WRX's have the same gear problems.
Next time I am going to drive as many WRX's I can till I find one that shifts good.