pepe is correct in that all soil quality is determined by the worm presence and that all mulching of any kind will increase the worm presence.
I used to have my mates dropping in wanting to dig up my yard for worms to go fishing with until I said to them.. “here take this old wheat bag and toss it down on your back yard and keep it moist.. grow your own worms and leave mine where they are.”
It is also true that the breaking down processes do use NPK and in many cases can actually cause a lock-up off these important elements or other trace elements. The chemistry of our soil is something each gardener needs to learn in situ .. on their site. I often deny having a green thumb.. I usually say.. “nah.. look my thumbs are brown.. not green.”
A mulch solely composed of rice husks for example, will indeed cause such a scenario. The Ph of the soil or the mulch is an important consideration. It is basically impossible to alter extreme Ph situations for very long. As indeed we can only affect the top or the surface of the soil, for brief periods of time. However, altering the soil surface with mulch can and does create a more complex soil biology which in turn affects the balance in soil chemistry.
Manures are fertilisers or soil conditioners depending on how you use them. All fertilisers can alter the soil chemistry either briefly or for longer periods.
Soil chemistry is important to be kept in balance with the needs of the soil biology. It is far better to aim at a healthy soil biology than to fertilise a plant growing in that soil. Fertilisers(many of them) can kill the microbiology in your soil which in turn can create a chemical imbalance.
It is important to become familiar with such things if you want to garden organically.. or indeed farm this earth at all.