I think you're misreading that.
There's a lot more than 1-68 to creating the field, yes. But that's really 90% of what the committee has to do.
From there, they feed that into a computer and that wrestles with all the rules they have for placing individual teams, moving teams up\down from their ideal placement when needed, etc.
It would be much, much harder to manually do all the things they need to do to create the bracket by hand. Hundreds of potential matchups you need to avoid. Any manual changes from the scenarios the computer creates could easily create a cascading effect where you create more bracket issues with each change, so they would likely avoid that.
They’ve had the committee speak before about what is entailed with the selection process. They do create the matchups and regions manually. Now I’m not saying computer data isn’t involved, but it’s done by the committee.