Core recovery files for the Team Win Recovery Project (T.W.R.P) - this is not up to date, please see https://github.com/TeamWin/android_bootable_recovery/
I tried this on a completely stock N7, unlocked it, and then flashed via fastboot. It does indeed boot loop after failing to mount /data, as does twrp-3.0.0-0-flo.img. Restoring to stock, rooting, and then installing using the official play app works fine as reported on XDA.
I noticed this thread on XDA reporting that it is not possible to install twrp-3.0.2-0-flo.img on a Nexus 7 2013 (either model) via fastboot:
https://forum.xda-developers.com/showpost.php?p=68426857&postcount=674
I tried this on a completely stock N7, unlocked it, and then flashed via fastboot. It does indeed boot loop after failing to mount /data, as does twrp-3.0.0-0-flo.img. Restoring to stock, rooting, and then installing using the official play app works fine as reported on XDA.