Stencil layers operate on all layers below whereas a matte effectively operates on one layer, modifying/ replacing its transparency. Not sure what other explanation one would need - since a layer style is applied to a layer, it has no way of knowing what happens after it has been blended with 20 layers above it, so it cannot determine any contours for layer styles other than its own.
I'm looking for the technical reason and I don't think what you're saying makes that point.
I don't agree that a stencil is a group of layers while a track matte is a single layer. Both combine layers. In addition, Track Mattes work only on the single layer above the layer with the Track Matte applied not on 20 layers. Perhaps you are referring to blending modes.
In addition, Track Mattes work only on the single layer above the layer with the Track Matte applied not on 20 layers.
I never said something else.
I don't agree that a stencil is a group of layers
They are. Stencils operate on comp buffers, mattes on layer buffers. It's simply tech stuff. Accept it as it is. No point in going insane over such minutia. Layer styles are pretty useless most of the time, anyway, due to how they are applied.