inventory preload question


Reading the documentation about this feature, I'm trying to understand how this works. Seems simple enough, but it's confusing how Jamf implemented this. I believe once the proper CSV file is uploaded, most data is not loaded until an inventory update is run? Is that per a device? ("Computer and mobile device data, including the device location, is applied on an ongoing basis each time inventory is collected".) Also it seems it always takes the preload data over any changes. I.E. If I have a department set for a computer in inventory preload, inventory update is run, then edit the department in user and location page, at the next inventory update the department will be overwritten with the department from inventory preload, is that correct?
Also the inventory preload does seem to load until the computer is enrolled? When uploading the CSV it shows up in activate data, but the computer is nowhere to be found in when searching inventory.