Do built-in knife sharpeners in the block actually work?

Reviewers are split. Many verified-purchase owners of the Ninja NeverDull and McCook systems praise the convenience, but the r/sharpening community is skeptical, with one thread nicknaming one system 'Alwaysdull' and noting pull-through sharpeners remove a lot of metal and don't match stone sharpening. The consensus: built-in sharpeners are convenient for casual cooks but not a substitute for proper sharpening if you care about edge quality.