I think SCMurphy's take is similar to my own on this.
Both he and I, as well as many many others long before us, used all sorts of DIY versions. I cannot even count the number of sediment versions I've done.
I think if you include variation with DIY methods, trying to find a standard method so that folks have a higher level % etc of success and streamline advice etc, the trade offs of inert vs N/P enriched sediment types, ADA comes out ahead.
Many balk at spending $$$ for ADA AS. Fine. If you live near a good source of wetland sediment, you can go collect it and wash it, screen it and let it soak for a few weeks, or DIY any number of combos, but these all take a lot more labor a work. A lot more.
So you can DIY the work yourself if you chose, or just pay for4 it and have the ADA As look nice also.
Sort of like buying a glass tank vs DIY a glass tank.
Why not make those since it is much cheaper to DIY a glass tank?
Nutrient rich sediments do offer some good trade off benefits, but inert sand works fine as well and you can add a few things to that to help, eg osmocoat etc, peat, some mulm. All things I've used going pretty far back.
You can also add less soil, not as much as suggested in many cases.
I think what happens many times is that some think they can add everything they need into the sediment to avoid dosing the water column. While this is true, we can see it's limitation. We still are going to need to CO2, K+, traces etc. So it does not save you from labor or help the plants any better.
The water column dosing is also an issue if you forget or do not add enough.
So bring both sources of nutrients into the plan, you have a win -win situation, rather than this "either or" business. I have no idea why anyone likes to play those type of black and white games when common sense will quickly tell you if the water column is also fertilized, you have a much greater extended sediment nutrient source lifetime. And by adding sediment nutrients, you have less error with forgetful water column dosing.
Add less light, now you have less draw on CO2, and also less draw on sediment/water column nutrients. Now you are getting somewhere and this can apply to any method. Now you can get more out of the sediment with fewer failures.
I think many are still stuck in the past about nutrients in the water column somehow being "bad" and "causing algae", both of which have been patently and methodically shown to be false. If that is accepted as a cause, then if everything is truly independent, and NO3/PO4 cause algae, I should have algae and should have had it for decades. When folks claim otherwise, it quickly tells us that their tanks are not independent. That have some other variable that is causing the results for them to come out different and get an algae bloom. Some they try many things and keep claiming that NO3/PO4 causes algae.
Using lower water column nutrients is one such method.
But they have as much algae as anyone with high nutrients like myself if not more.
ADA AS has some trade offs, cost is the big one, lots of water changes(EI does the same thing here, so these match well together- see less draw from the sediment-extended life), but it's also much easier to tell new folks how to use it.
Many folks have different goals, so no one sediment will meet those goals, nor any one method, heck, I do not use one method myself.
What is key is a good understanding of each sediment, it's trade offs, benefits and what the user/newbie is looking for it their grand scheme end result.
Most want nice plants, most what some type of growth "rate"(slow, medium, high), no algae etc. So focusing on light and plant health achieves that, what changes really is the rate of growth they want and how much effort labor they want to put it for it to be a long term system that's stable and resilient.
I think nutrient rich (not Eco complete etc) sediments with some N and P do a good job there. Good texture like clays are also good(Kitty litter to ADA AS).
With DIY sediment methods, I think many need to do more water changes in the start, more focus on CO2, add some carbon etc, plant more heavily etc.
The same is true with ADA.
The chronic plant mover needs a more inert sediment, flourite/EC, sand etc.
If all you want is some N and P long term, add osmocoat. Cheap, last as long if not longer than ADA PS, less messy and tacky looking.
If you really wanna learn more about aquatic wetland sediments, buy or check out Reddy and DeLaune's Biogeochemistry of Wetlands, 2008.
One of the best all around text on aquatic sediments there is by one of the most active researchers in the field of sub and tropical aquatic plant sediments.