Well, there where a few precursors prior to PMDD:
Which was namely this:
Most folks did the second link as they had been doing PMDD prior and then took the rather large leap of faith at the time(you folks have no idea how folks went after me about this issue, it fundamentally disproved/falsified a long cherished hypothesis, but the proof was in the results).
Since folks where already dosing KNO3, K2SO4, GH, Traces, and many used daily dosing, all that was needed was some PO4.
So if you wanted to add less and dose with more precision etc and tweak subtle things more, then the above link would work nicely. If that was/is your goal..........
However, many did not have that same goal. Steve did not do water changes for 6 months, Dave did not do any for 2 years and they used the test kits etc to dose accordingly. That was over a decade ago.
But it sounded too complex(PMDD with liquids etc and dosing solutions), folks had to test etc.
I knew that using larger water changes reset my tanks anytime I mess up dosing or made mistakes. So If I did large enough water changes weekly, I could guess or estimate the rest of the week's dosing and simply reset at the end of the week.
I also knew large water changes help plants, algae do not like them, keeps the tank clean, makes the tank much much easier to prune and clean/work on etc. I knew that most all aquarists know how to do a water change and that requires no chemistry or complex stuff.
Teaspoons are easy and simple to use vs a scale. I just estimated based on 20 samples, the weights of 1/4 teaspoon and then tried several brands of teaspoons to be sure they where close using a lab scale.
From there I could get an error range for the teaspoon method.
When some folks claimed that this was inaccurate and sloppy on another forum some years ago, I lamblasted them because I've already measured the error and know the results, I knew them 10 years ago, long before most of them even kept plants.
It's irritating when folks make poor assumptions, it's even more so when they obviously have not done the measurements or test to prove their statements which are derogatory and bad mouth other folk's research and methods without any support. I support what I say, try it and test it. Then think about it, then go back and do it again, and again etc.........
That takes work.