Production and inventory are two different quotations
A production estimate describes work that has not happened yet: people, days, equipment, locations and post. It can be rescheduled, rescoped and revised, and its main risk is that the work takes longer or costs more than assumed. An inventory quotation describes access to a date: a slot, a page, a placement, a sponsorship window. It cannot be rescheduled and it cannot be recovered once the date passes.
These are not variations on a theme, they are opposite commercial shapes, and the fields that protect you differ accordingly. Production needs a schedule, rate bases and rights terms. Inventory needs dates, positions, deadlines and a make-good position. Businesses that run both through one undifferentiated pipeline tend to underprice production and lose inventory revenue to material that never arrived.
