Nowhere does that require you to go and get a DUNS number, which is onerous for a single developer to do without the infrastructure of a company.
It seems kind of odd to me to rely on some kind of external hidden "credit agency"-style company for this? And why would DUNS want to know about some kid in their basement in Bangledesh making (non-malicious) apps, and why would the kid want Dun & Bradstreet to know about them? It makes no sense at all.