One of posters has a DIY for Pfertz using the bottles.
Most liquids are dosed for CO2 enriched aquariums daily.
This is because they tend to be pretty dilute, or, a bottle of water, with a tiny bit of ferts in them. This works well for smaller aquariums (gives you more accuracy, not that it is that critical
however.) but gets tiresome for say a 180 Gal tank.
EI can be modified to make your own DIY liquids however you chose
. You can match commercial brands, or go richer, you can also dose 2-3x more every other day if you wish.
Simply because you use ferts diluted in water or not, or richer or leaner, does not imply a proprietary "method". These are choices humans make for management. They have little to do with a "brand".
Most add more/less than the suggestions and tweak to their liking, few follow them to the "letter of the rule"
That should not hurt, but tends to be on the much more conservative side for virtually all brands.
Since different light durations/intensity polays a massive role in the growth rates and thereby demand for CO2 and nutrients, you will get wide ranges of reactions and blame for nutrients being the blame of all things evil. Likewise, CO2 usage is rather poor , particularly among intermediate/newbies and even advanced folks time to time. This can affect nutrients uptake as well and have led many to blame nutrients for all that ails them.
In other words, it's not all about nutrients, they are rather easy and simple.
Add X amount to X amount of water by X amount of time.