Think you nailed it by breaking it up by groups of people with different lists. Literally every group/dept/team has a list. Someone/process has to arrange that

Think you nailed it by breaking it up by groups of people with different lists. Literally every group/dept/team has a list. Someone/process has to arrange that into a single list for the group that builds. If you have more than one group that builds stuff, then more output lists and more complex the transformation from input lists to output lists. Guess this is a simplistic summary of what PMs and Eng managers do.