Thanks for all the replies. I especially was interested in the "how do they cut them" when a factory makes up the pre-cuts. I'll search for that video. Thought there would be more of a "no error" method that would eliminate such differences.
I love the continuity of fabric line going together nicely in a project. The pre-cut packs eliminate the oopsies of choosing a fabric that just wasn't right with the rest. The downside I've found is those couple of "unfortunate choices" that just don't appeal to me.
I love the time saving feature of pre-cuts and find many ideas that I love to use them for (mostly from Jenny Doan).