I seem to remember CyanogenMod having a per-app sandbox feature around 2013 that returned blank info from a virtual root.

Like many point out, this isn't data poisoning, especially if there aren't metric-breaking honeypots around the web seeding these services with enough noise to make these collection practices useless, which there are not.

A more effective alternative might be hashing real contacts to generate seeds of complete but false profile information. Apps thinking they got the mother lode wouldn't be able to assign confidence to any results they didn't have duplicates of, and slowly over time, groups who used this would become worthless.