Low-entropy initial condition: boundary condition or dynamical explanation?

Question

When it comes to cosmology's arrow of time, it's common to refer to the low-entropy beginning of the universe to define an initial boundary condition.

My question is whether the low-entropy beginning is truly best understood in terms of a fundamental boundary condition or if there are physical dynamical models capable of explaining the low-entropy beginning of the universe without presuming such a special initial condition.

To date, I am most interested in whether existing models in cosmology or statistical mechanics have reproduced this low-entropy beginning without the use of special initial conditions, and if so what mechanism they employed.