Getty Images Select auto-lending numbers may finally show an industry that is tightening credit extended to the riskiest borrowers, but that doesn’t mean there’s been a healthier turn for the bond-like securities tied to a stretch of loose lending post-recession. In fact, subprime auto bonds issued in 2015 are by one measure on track to be the worst performing across the history of car-loan securitizations, according to Fitch Ratings. Securitizations are built from bundled loans and resold as...