Mounting will no longer be available in any recovery because the internal storage is formatted as ext4 whereas it use to be FAT on the LTE. The latter is USB mountable, the former is not.
The closest you can now get to this functionality is to use USB-OTG.
Sent from my HTCONE using Tapatalk 4
Device: Sprint HTC One | Hardware: 0004 | Software: 1.31.651.2
Radio: 1.00.20.0626 | PRI: 3.17_003 | PRL: 55015
Bootloader: S-OFF LOCKED | Hboot: 1.44.0000 Jul 5 2013
Recovery: TWRP 18.104.22.168 | Kernel: 3.4.10-g30a4e11
ROM: Stock w/ Disable Write Protection and Power Saver Removal