Well, that’s what I would like them to be able to do.
The age verification plugin asks for explicit consent. When a visitor goes to a page that’s age-restricted, the verification screen comes up and says clearly, “This will place a verification cookie on your device.” If they then update their preferences and that cookie goes away, that’s great, but it doesn’t make any sense if updating the preference makes them unable to voluntarily set the verification cookie next time.
If it did that, the next time they tried to go to an age-restricted page, the verification just wouldn’t work (the plugin would be unable to place the cookie even when the user said okay), and I don’t know how to set it to return an error message beyond just not working. (I didn’t design this plugin and I’m not a developer!) That seems extreme, since the cookie is only being placed through voluntary action.
Similarly, if they leave a comment and check “Save my name and email,” it’s fine if updating their preferences deletes that cookie, but it seems logical for them to be able to set the cookie again by clicking that box the next time they leave a comment. If the changed preference not only deletes the cookie, but blocks it from being set again, the box will still appear, but it simply won’t work, and a technically illiterate user (like me!) may not know why. Again, that seems unnecessary from a GDPR standpoint. That box isn’t pre-checked or required, so I’m not making them save that information and they’re perfectly free to leave a comment without it if they want.