Currently after enabling the option 'Remind Users to change password', all scoped users are opted-in to receive those notifications by default. Meaning, the end user needs to manually opt-out from them in the PMUser site if they do not require/want to receive those notifications.
Instead of having users to "opt-out" you may prefer to have users to "opt-in", in case they want to use this feature; the option would then be available to all users and when needed they can manually activate it.
An enhancement request (TF00707620) has been created detailing the feature referenced above.
The product team will evaluate the request and this feature may become available on a future release of the product.
Please refer to this article for updates or contact support referencing the Enhancement Request ID: TF00707620.