Wccftech confirmed with 2K that support for HDR displays in Borderlands GOTY and Borderlands 2/The Pre-Sequel UHD packs won’t be available on PC, only on PlayStation 4 Pro and Xbox One X.
Source: N4G PC Borderlands GOTY and Borderlands 2/TPS UltraHD Packs Won't Add HDR on PC, Only on PS4 Pro and XB1X