Correct me if I’m wrong but are they not potentially two different things (although reliant to an extent on each other). Your deer management plan would set your medium / long term aims along with all the options to meet these aims, not only shooting the deer. Your aims could be to protect crops, re growth, newly planted trees, SSSI’s and or to maintain a deer population for venison or paid stalking. Your Cull Plan is the way you meet your aims. If a farmer with a couple of hundred acres on which he has some newly planted trees and is concerned about the crop damage might want a Deer Management Plan. This might include a recommendation by you for fencing to protect the new trees and the sighting of high seats to deal with the deer coming from the adjoining farms.
Your subsequent cull plan will then be designed to meet your aims. Most of us have come across farmers who just want the deer gone. What and when you shoot it, from a management point of view, needs to reflect what you need to achieve.
If the land owner wants a management plan, I would, within reason do one even if it was very basic.