how hard can you turn a STOCK 5.0?
Yeah, but that was with heavy stock cast pistons and rods, and poor material strength. What year was this 302 crank recommendation from? Piston tech improved considerably from the 60's and 70's
Speed is important, but speed means nothing without mass. High tensile strength rod bolts, lighter than stock rods, light hypereutectic pistons, all make a difference with my motor. Yes, there will be no point in revving a stock 5.0L past 5500RPM with those heads, but with upgraded rod bolts (material, not size, you weaken the rod too much with bigger bolts) and a decent balance, you can easily turn 6000 RPM and more.
I don't think Ford used a forged crank in the 289 Hipo, and those things would rev, especially with the solid cam.
I am not questioning your experience at all. Having a disagreement doesn't mean I think poorly of you.