The above article pre dates EI.
I was finding most folks where not doing their testing and with the water change re sets, we did not need them.

As we became more comfy with this method, we later started exploring the upper ranges rather than looking at near limitation levels.
Much higher lighting intensities became more common also about that time.
Since then I've extended the ranges and uptake rates and taken out the test kit altogether.

You'll note I suggest testing and referencing with high quality test kits, not cheap junky test kits.

Some have criticized me for changing my mind over the years........
Well, I keep learning and improving as I hope everyone does as they go through life.
As I get tired of doing extra work and apply this in a practical way, then EI starts to make much more sense.

PPS folks seemed to miss this is point and the history, as this old article essentially is what PPS is with water changes. Dave Gomberg and others also did not do water changes for sometimes up to a year or two either using this type of method and level range.

EI is much newer in this context than PPS as the above article pre dates PPS by about 6-7 years at least. The main tenent for both is using test kits to maintain a dosing routine with ferts at a prescribed level.

You can spin and talk all day about differences, but it boils down to that basic method, thus it is hardly new and hardly something myself and other have not explored in depth pre dating anything written about PPS. See PMDD for daily dosing routines with or without test kits. ADA also suggest adding daily nutrients etc and did so back in the 1990's as well.

Some subtle difference can occur when folks pay more attention to a tank, regardless of the method, when they dose more frequently and do not skip dosing.

EI is different because it throws away the test kit and used habits already in place in the hobby. This re set method allows better confidence, less $ for test kits, equipment and less technical know how not to mention much easier trouble shooting.

So when folks see my past history, this will help them to understand why I suggest EI over the older version of the a List of Levels and Parameters.

I do take a bit offense when someone suggest they have come with something "new" and that the EI is bad, old, sledge hammer method, blindly throwing ferts at toxic levels and other hyperbole and outright lying. I've been down both paths quite some years ago.

I also bring this up for another reason, I started suggesting EI over this older method here above with good reason: it works better, it's easier to help others with issues, makes things easier for folks and their habits.

Asking someone to buy all these test kits and chase after the ppm's?
Make all these solutions? Dose and maintain these ranges?

You need not be a scientist to see the simplicity in EI.

Can you do leaner versions of EI?

Certainly.
Many do.
Erik Leung did some leaner EI style methods as did Jeff in out local club. Some dosed it daily, some 2-3x a week.

Plants can and will grow in leaner more frequently dosed tanks as well as richer dosing as well, neither tank if you follow a method correctly will grow plants very well.

If you fail at one method, it does not imply the method was at fault, perhaps your habits did not fit well, there are many reasons for failure, but we know that PPS, ADA, Dupla, EI, The List of Levels and parameters, PMDD...they all work well and can be done to high level.
Thus one can only conclude that the method does not fail, we do.

How to do a method easily is really a trade off. What areas should be considered and will be problematic? Most hate water changes and most hate testing.

So should we all go non CO2 methods which require neither for good long term success?
Well, plants grow a lot slower, some ask for that, so yes, the arguments for that method are also very strong indeed.

Still, I know that each method is successful and can be done well, having mastered each of them.
If you have not mastered them fully, then you may be led to assume that a method is bad or worst than another.

Such thinking is rubbish.