While black hole mechanics suggest that the entropy of a black hole is limited by the Bekenstein bound (3), it is known that the usual classical entropy of a system can be expressed in terms of its microstates:
Since in Section 5.1 it was explained that the horizons just hide matter, and hence entropy, and are not in fact the carriers of the entropy, it seems more plausible to me that the structure of the matter inside the black hole is just bounded by the Bekenstein bound, and does not point to an unknown microstructure.
Similarly, in Haranas and Gkigkitzis , the authors examine the Bekenstein bound of information number N and its relation to cosmological parameters in a universe, where in Gkigkitzis et al.
Our result is in agreement with that of Lloyd  and Davies  where the author predicts that this is equal to the maximum number of bits registered by the universe using matter, energy, and gravity, and it is found with the help of the Bekenstein bound and the holographic principle to the universe as a whole.
Gkigkitzis, "Bekenstein bound of information number N and its relation to cosmological parameters in a universe with and without cosmological constant," Modern Physics Letters A: Particles and Fields, Gravitation, Cosmology, Nuclear Physics, vol.
This maximum is known as the Bekenstein bound, being the upper bound on the entropy and thus on the number of bits of information that a given volume with finite total energy can contain.
The Bekenstein bound is undoubtedly a force to be reckoned with.
In 1972, Bekenstein wrote a seminal paper showing that the entropy of a BH is exactly proportional to the size of its event horizon; then, he showed that there is a maximum amount of information that can be stored in a finite region of space, a concept known as the Bekenstein bound