Finally, whether or not it's tidal forces comes down to an interpretation of how one decomposes the Riemann curvature tensor. In some ways, the Weyl tidal tensor part is good for understanding the disc's warping and tearing. However, if one decomposes the fluid into a zillion particles of dust, this approach seems (to me) to be less intuitive (and certainly harder to compute) compared to the GRMHD approach in the paper. Additionally, for these effects the black hole's spin parameter is more relevant than the black hole's mass, and notably the paper is concerned about quasars and other active galactic nuclei, which implies supermassive black holes, so the tidal tensor will in general be quite gentle even at the ISCO.
For none of the above do we need to know anything about the microscopic states within the horizon. This is entirely about solutions to the geodesic equations and equations of motion in the spacetime outside the horizon, and matter-matter interactions of disc material (or "figure-skater-like spacecraft" material).
Finally, whether or not it's tidal forces comes down to an interpretation of how one decomposes the Riemann curvature tensor. In some ways, the Weyl tidal tensor part is good for understanding the disc's warping and tearing. However, if one decomposes the fluid into a zillion particles of dust, this approach seems (to me) to be less intuitive (and certainly harder to compute) compared to the GRMHD approach in the paper. Additionally, for these effects the black hole's spin parameter is more relevant than the black hole's mass, and notably the paper is concerned about quasars and other active galactic nuclei, which implies supermassive black holes, so the tidal tensor will in general be quite gentle even at the ISCO.
For none of the above do we need to know anything about the microscopic states within the horizon. This is entirely about solutions to the geodesic equations and equations of motion in the spacetime outside the horizon, and matter-matter interactions of disc material (or "figure-skater-like spacecraft" material).