I was always under the impression the “aged forest products” were just the leftovers from logging and milling that couldn’t be sold or used as wood. Sawdust, reject boards, rotted limbs, etc.
Several years ago I started to research the "Aged Forest Products" and similar terms as shown in the ingredient lists on the backs of bags of "soil mixes". And, the terms are not just on the bags at hydro and grow shops since they will be found on the bags of composts and soils in gardening supply stores for the general community.
Yes, the "Products" can be logging leftovers since the foresters on federal and state forests do not want piles of slow decomposing wood pieces. So the stuff gets hauled off to companies that will start to turn it into compost. Then when the logs get to the sawmill they are debarked producing more scrap. Then the piles of sawdust after 'debarking the logs'. Then the sawdust piles can be added to the compost pile along with the reject wood. More likely than not it is more economical to pay someone to haul all this stuff away rather than try to have sawmill employees properly dispose of it.
I literally spent several weeks looking at "web page searches" getting a better picture of what types wood and scrap was gathered. There were several open pages on my web browser, each with its own question or search term at the top. That lead to researching the commercial composting businesses, often called farms, that built the huge piles and maintained them.
Once I started following the rabbit holes about commercial wood composing it became interesting. There are some very large companies that are responsible for composting huge volumes of wood products. I saw photos of compost piles that were as wide across and as long as a typical city block and as high as a 3 to 4 story house. And next to it was another one that was still having wood chips, etc dumped on it. The companies had the composting figured out and able to say that it took 2 years start to finish.
Just about any tree scrap was taken whether from logging operations, saw mills cutting logs for boards or tree trimming or removal companies.
Interesting thing I picked up that changed my thoughts on what wood to get was that they mentioned they looked for pine scrap because it was beneficial to the mix and it helped to speed up the composting stages. I followed the pine tree wood scrap and found out that the pine contributed a enzyme or two that helped the process but the big thing was that pine had a better amount of sucrose or sugars that did an excellent job of feeding the microorganisms that ate the wood. I was not able to find what was added to the piles to help the process other than it was a Nitrogen source. Just found references that it was done.
In the end I have to figure that the bags of soil we buy at the store are mixed by the company on the bag. But, the compost itself that is inside is supplied by one or more of these composting farms. Most likely they put out specification sheets and the compost operation will supply the end product if it meets the specs.
All this because some in the group kept complaining about the small amounts of sticks and incompletely composted wood chunks. In the end I called one of the large companies. They gave me the best time to call, the name and the phone extension for the person in charge of their wood composting division. Next chance I go I called. It seems that the amounts of sticks and pieces are actually allowed there by both the composting business and the company bagging the final mix. The big thing is that the wood is composted far enough along that it acts as a sponge and helps to hold moisture and the micro-organisms live in those pieces of wood.
I am now making my own "Aged Forest Products" compost for use in my potting soil mixes.