My suspicion is that he feature you activated that originally created
these lists was never designed to be activated independently from the
site definition that it was part of. The problem is that the lists
probably support some other functionality that was installed by the
feature. The designer evidently never designed a deactivation for the
feature since it was a required part of the site. So the way the
designer planned for you to delete the lists and feature was to delete
the whole site. Since you've installed it on a separate site manually I
suspect the only clean way to remove it would be to delete the entire
site where it is installed. Even if you find a way to delete the list
instance itself you may not get all the things that it created in the
site. That could lead to a site that begins to throw mysterious errors.