Still a newbie myself but Definitely have some input. From my understand we can really grow In anything we want too, each medium just comes with its own draw backs ?
Forest soil I'm sure is great for moisture, and some organic natural ingredients. But it could come with pests, diseases , fungus or many other things that could come with each scoop. Also you wouldn't "know" exactly what is in the soil. Making feeding later on more difficult.
Another thing could be drainage. You would have to add some sort of perlite or high drainage medium to help the water get out.
Overall I wouldn't recommend it. But again I'm still a newbie and what do I know !!
Sorry if I rambled.. Just trying to get everything out that I think about the subject !