My experience varies depending on lifts. Squats for example I hammered away at 80% for nearly the last 3 years and made absolutely zero progress. Bench Press I spent the last 2+ years training around 80-85% and added maybe 10-15 pounds to my total. I did a lot of sets around these percentages for both lifts. A lot. Didn't help me a bit.
Deadlifts are a different story. Last year I dropped 80% work and focused only on 20 rep sumo sets for quite a long time. When I came back to conventionals I started to destroy PRs like crazy. My max went up my about 60 pounds in 6 months and I didn't work above 80% until the final month or two before my meet. I will add that I starting using a ton of speed work during this time, and began attacking the bar, and I think this was a major contributing factor ion my progress. Also, perhaps the rep work helps my glute and hamstring weaknesses.
My opinion on 90% work has changed a lot this year due to personal experience. I have made better progress in 14 weeks on bench and squat using more frequent 90% work than I did in years without it. I am not educated enough on all of these programs to comment much. I have read them and know what their percentages look like, but have never tried them.
I will say that I believe some form of 90% work is needed once you hit hard walls. How frequently this is required, I am not certain of yet.
I also want to add that there are other variables at play in some of these programs...frequency, volume and with some overreaching.
Korte, if I remember correctly, starts with high frequency and moves towards intensity. I believe in Phase II it adds heavier work on Fridays.
Stephan Korte?s 3×3 Powerlifting Program - Muscle and Brawn Bodybuilding, Powerlifting and Muscle Building.
Coan-Phillipi adds 85% work fairly early in the cycle.
My only point is that Sheiko and Korte introduce variables other than intensity. And I think both Coan and the Ortmayer program have you with some 85% work on week 2 or 3. I think the Ortmayer has 90% at week 2, correct me if I am wrong.
Anyway...just floating out some info and random thoughts.