As explained in the issue.
optUserOut is called, it should set the
forgetUserOptOut then it should only undo the previous action and remove the
mtm_consent_removed cookie. It should not set a
consent given cookie because the user did likely not really give proper tracking consent (they would then instead implement https://developer.matomo.org/guides/tracking-consent ).
Noticed this while implementing a custom opt out screen for Matomo for WordPress