I took PF171 to mean that Q is quoting an old Comey email.
"Untethered" is a fave Comey word. One tends to have those.
Check the dates. December 16 - This was an email (or draft email back and forth) picked up in the Google operation a few weeks ago.
Do we know what "shelter against the PDB" means.
The PDB seems to be something (((they))) want to protect.
PlanDB
…DataBase?