Throughout 15th century art you see a style of dress most commonly worn on younger women and girls. It is a fitted kirtle with a wide open front. According to this theory the chemise beneath the wide front lacing is covered up by a placket worn UNDER the kirtle, rather than over as with the placket theory. Thus, when the Burgundian gown is worn over the kirtle, the placket from under the kirtle shows at the neckline and the kirtle itself shows at the hem when the gown is lifted.
Some people have theorised that the wide fronted kirtle is simply a style for younger women and girls, this theory suggests that women of all ages would wear this dress however grown women were less likely to wear it without a gown over the top.