Full Answer
All three are simultaneously correct and incomplete. Facebook reports 26% higher conversions on average than analytics tools due to modeled view-through attribution (Varos, 2024). Google Ads over-attributes by 15–20% when Enhanced Conversions modeling activates. GA4 underreports paid conversions by 18–35% when cookies are blocked. The framework: use your WooCommerce order count as ground truth, then measure each platform's self-reported number to calculate a tracking gap per platform. A critical hidden issue: GA4 data-driven attribution requires 400+ monthly conversions to activate — most WooCommerce SMBs never hit that threshold, so GA4 silently falls back to last-click with no warning. Server-side tracking ensures all platforms receive the same event data; discrepancies then become attribution methodology differences, not unexplained data gaps.