The hard part about understanding all these pedigree patterns is there's no right and wrong way. Every pedigree pattern has worked in the past at one time or another. It's just that many pedigree experts have found out that some patterns work better than others (as a rule).

You also have to take into consideration WHO the horses are in the pedigree, and not just focus on a couple of famous ancestors. The mare line is important (tail female line); the sire's mare line is important; the broodmare sires in the pedigree are important; the sire line is important; the sibling relationships are important (as well as where they are in the pedigree)...and the combination of certain lines is important. There are a lot of components to study in pedigrees. Combine all that with knowing phenotype, and selecting for performance records/earnings on horses you're breeding to, setting your goals, and you can see why so few people actually breed a great horse. A lot of that can be pure luck, too.