If the default setting is to enable the feature, then the feature isn't opt-in because the user didn't "opt" (ie, choose) to enable it. For a feature to be opt-

If the default setting is to enable the feature, then the feature isn't opt-in because the user didn't "opt" (ie, choose) to enable it. For a feature to be opt-in, the user must explicitly choose/opt to enable it. Otherwise, the user didn't opt for anything and if you enable it anyways then the choice to be made is to opt out.