I ran 847 VP-and-above profiles through a two-vendor enrichment waterfall over six weeks, and the mobile hit rate gap between using one vendor versus two was not subtle — it was 31 percentage points. That number is what pushed me to write up the method in detail. The core problem with B2B mobile phone number enrichment for VP and director titles is not that the data doesn't exist. It's that no single vendor has comprehensive source coverage at senior seniority bands. RocketReach and People Data Labs (PDL) have meaningfully different provenance graphs — PDL aggregates heavily from professional networks, data partnerships, and self-reported professional profiles; RocketReach derives significant coverage from verified-contact exchanges and contributor networks. They don't pull from the same pipes, which means combining them produces genuine lift rather than duplicate noise. What the competing guides miss is the sequence . Everyone talks about waterfalls in the abstract.…