Back in the early 2000s, I saw a movie on the Sundance Channel called Dresden. It was only rated TV-14, despite the fact that it had several uses of the f-word, as well as two FULL FRONTAL nude scenes involving the female lead character. Not the sort of thing I would let a 14 to 17 year old watch.
Another one that seemed too lenient was NYPD Blue, which was only rated TV-14 despite containing harsher language, nudity, and other adult content than what was typically shown on broadcast television. Other TV-14 rated programs seen on broadcast television at the time had far less serious adult content.
There is no single authority that decides TV ratings (unlike the MPAA, which decides the ratings for all theatrical movies); the TV ratings are left up to the TV stations, broadcast networks, cable channels, and syndication companies to decide, so there's bound to be some inconsistencies.