Once connected pawns reach the sixth rank with the king supporting them, the defender's king and bishop can no longer cover both advance squares and the pawns break through.
The pawns have reached d6 and e6, and this is the decisive difference from the previous drill. The advance squares are now d7 and e7, one of each colour, and the black king on e8 cannot stand on both. Black's dark-squared bishop on h4 cannot help on d7 (light), and the e-pawn's advance to e7 is protected by the d6 pawn.