The default effect describes how a starting option can persist because changing it requires effort. A prechecked control is therefore part of the decision path, not merely decoration.
The demo alternates which notification option starts selected and moves an illustrative choice indicator. That indicator explains the mechanism; it is not observed customer data.
Do not infer consent from a prechecked box where explicit agreement is required. Make alternatives easy to find and measure actual choices.
When to use
Review defaults in onboarding and settings against user benefit and consent requirements.