Now if you're after mycorrhizal fungi what you're looking for is AMF (arbuscular mycorrhizal fungi).AMF is a type of endomycorrhizal fungi (penetrates plant cells) that pairs with 80% of land plants including cannabis. There's a few strains of AMF you propably know already ie. Glomus intraradices, Glomus mosseae, ect. It can be found growing directly on plant roots - it doesn't grow without a host plant, so you won't find it in multiplying in compost, manures and teas (that's saprophytic fungi you see). Because of this dependence on a host plant, AMF is more expensive to produce as lab techniques can't multiply them effectively (the spores can be manipulated but they will not complete their life cycle without a host).
On the other hand Ectomycorrhizal fungi (what's loaded in a lot of "myco blends") doesn't pair with anything but certain tree species Ecto can be propagated without a host plant so it's cheaper to produce. That's why resellers add it -- to look like more props per container. Some shady stuff going on.