Contextual/Bible study argument: Ronald Pierce and Rebecca Merrill Groothuis claim Paul only reinforces 'source/provision,' not authority

Ronald Pierce and Rebecca Merrill Groothuis, in 'Discovering Biblical Equality,' argue that though kephale in the head-body metaphor 'may connote authority over or source of provision,' in the larger context of both Ephesians and Colossians, 'Paul only reinforces the idea of source or provision for husbands to wives.' Mike notes they acknowledge head could mean authority, but assert Paul never uses it that way.