The device maker could ship with programmable proprietary firmware and have the possibility of being RYF-certified in the future if someone writes free firmware. Or they could ship with proprietary firmware in ROM and be guaranteed RYF certification immediately. The rules encourage them to pick the second option, and it's no surprise that companies such as Purism have done so.
Yet that option is never better for user freedom, since making software un-upgradeable does not make it any more free. And occasionally it is worse, in the event free firmware becomes available later on.