You can use Prelipin's table as a general guidline in designing a routine. It lets you know how to get a productive workout with various weights and percentages. For example, if you want more bar speed, you can incorporate a speed workout, with say 60% of a max. So, if you can squat 500lbs, that's 300lbs if you go at 60%. If you do traditional sets at 300lbs and you squat 500, you are basically wasting your time.....BUT, if you do them as explosively as possible and do say 8 sets of 3 reps with no more than 45 seconds between sets, you can help your bar speed for the heavier work, provided you still do heavy work on another day.
Also, with a Bill-Starr type of program, the 'light' day is great for recovery. Say you squatted 500x5 on Monday and are sore, then Wed go 300 for 5x5 wih about a minute between sets, work on bar speed and it serves as active recovery too.
Another way the table can be useful is for workload.....Say you do 5x5 on squats with 365, your total workload is 9,125. The next workout, you feel you have apsolutely hit a wall, and if you tried 5x5 at 365, at most you'd match it, and most likely see a regression, you can deload if you feel it is time.....or you can keep upping the workload, but change rep schemes......say you do 5x3 at 385, and then 345x12, for a total workload of 9,915....you up the workload by playing with the reps and keeping yourself 'fresh', so to speak.
As far as the 7 reps being too many. I both agree and disagree, and I hope this makes sense how I explain it. I don't generally agree with a statement worded like that because who is to say what magic number is too many for all people. I do, however agree that in most cases 4-6 reps, is a great range of reps for jut about anybody to progress nicely on. The idea that more than 6 reps is too many for strength is based on the theory that the CNS is shot after 5 reps. Again, people can progress with 10's and 8's at times, I've personally seen it and experienced it, so take all the science for what it's worth. Put in your time under the bar and draw your own conclusions.
I personally think prelipin's table is a great tool, but that's just it, it is a tool to help you, don't regard anything as the final word. Zatsiorsky is THE MAN.....so is Bill Starr if you ask me, they worked with the masses and got results, STILL, all people are different, and when working with different people, tweaks and changes are a must. All great coaches, teachers, and trainers realize this, that cookie-cutter approaches are a lazy approach and if you want peak performance from everyone, everyone deserves individual atttention. A successful coach like Zatsiorski or Starr knows this. A template is just that, everything is open to personalization. Just keep putting in time under the bar. texts are great for templates, and also for understanding anayomy, physiology, and biomechanics, to teach yourself the science.....but the only true way to apply it is on the individual......see what works for YOU.