I think this list speaks to a couple of things: first, the unpredictability of stardom or even MLB promotion of prospects -- high-ranked guys like Swihart and Margot, even Marrero (once considered #5 at a time when the farm was loaded), who made The Show but fell out of favor; and second, 20 guys from one farm with at least a cup of coffee in the bigs is a credit to any organization.
In a pennant race, prospect depth affords a club possible call-ups or more likely, trade options when upgrades are needed. Dombrowski deftly used these resources to do his job and build a champion... and if you read Speier's book, Homegrown, while it sometimes hurts to lose a youngster, even scouts and front office types that draft, sign and develop a kid are proud when the return helps them win.