Unreliability only works if it is discoverable. The audience has to be able to reconstruct what actually happened from evidence the piece supplied, otherwise the reveal is not a reveal, it is the story admitting it was misleading and expecting credit. The rule is that a second viewing should be more coherent, not less.
The interesting versions are not lying. A narrator who is self-deceived, limited, or defending themselves is more useful than one who is deliberately deceiving, because the gap then characterises them rather than merely tricking the audience.
In commercial work the honest application is the testimonial where somebody is plainly describing their own behaviour more generously than the footage supports. It is charming rather than damning, and it is far more convincing than a perfectly consistent account.
What is an unreliable narrator?
A narrator whose account the audience comes to doubt. The gap between the telling and the events becomes part of the meaning, usually characterising the narrator rather than merely misleading the viewer.
What makes an unreliable narrator work?
Discoverability. The audience must be able to reconstruct the truth from evidence already given, so a second viewing is more coherent rather than less.