If you create an initiative and give it a start and end date then a feature created from that initiative will inherit the start and end date of the parent initiative. Nothing wrong with that, but at the same time the features estimate will be set to the total length of the initiative and can not be removed.
If you add features to an initiative you and up with features that have an (unrealistic or simply wrong) estimate and can not easily be recognized as unestimated.
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As you described, it's true that when you create a feature from an initiative, that the feature inherits the start/end date of the initiative.
However, it is possible to remove this from your feature. By hovering on either of the fields for the feature, you'll see an "X" to the right of the field. Clicking the X will remove the estimate from the feature.