A suggested third model is a convective1 flow that mobilizes liquid fat from the filling into the shell due to pressure differences.
A convective flow that replaces the liquid fat in the penetrated fat matrix of the shell with the liquid fraction of the filling fat would lead to a BrTAG concentration rapidly reaching 2.7%.
Still, as the observed concentrations are above this level it suggests that more than the initial level of liquid fat phase is entering into the shell matrix.