How it happens
The call moves out of a conditional, into a different code path, or behind a feature flag. The call itself looks intact. What changed is when it runs.
What breaks downstream
Volume changes silently. A first-purchase event that used to fire inside `if (user.isFirstPurchase)` now fires on every purchase. Or a retention milestone that used to fire only after a real interaction now fires automatically. The event count looks fine; the meaning has changed.