This is audacious filmmaking! Photo-Illustration: Vulture; Photos: Max, Keith Bernstein/Warner Bros. Pictures/Courtesy Everett Collection An investigative documentary about preventable human error in commercial-airline crashes. A couples-counseling session. An experimental acting exercise. A reality-singing competition. A closely observed examination of male loneliness. A Mel Brooks–style Nazi satirical farce. In just the first two episodes of The Rehearsal season two, Nathan Fielder has proven to be a sexy bad boy of premium TV, bravely veering into whatever damn genre he pleases in pursuit of his great experiment, great entertainment, and a favorable “9” judge’s score. It works, and it never veers into...