Comment by conmod278

At sufficiently high energies, interactions that appear distinct at low energies may be described by larger underlying symmetries. Symmetries reduce the amount of independent information needed to describe a system. So the early universe can admit a remarkably compact description.

Regarding unitarity, an initial state does not need to contain a record of a history preceding it; unitarity only requires that subsequent evolution preserve the information encoded in the quantum state. Later states may contain enormously complicated correlations that simply did not yet exist in the initial state.

And there is no general principle saying that a large amount of quantum information requires a large classical spatial volume. A Hilbert space can support an enormous number of possible states even when its geometric description is extremely compact.

More importantly, the universe didn't emerge from a dimensionless point. The (t=0) singularity is the limit where classical general relativity breaks down and stops being a useful description, so the ordinary picture of information as some number of independent "bits" packed into a 3D space is no longer obviously applicable. A coherent theory of quantum gravity would probably be needed to really break further ground.