However, I have noticed that if "private" browsing mode is disabled,
"New Identity" doesn't actually clear any cookies anymore. It seems to
depend on "private" browsing mode being enabled in TBB to clear
cookies.
If that's the case then this is a bug. Providing a New Identity should
not be bound to the user being in Tor Browser's default mode or
allowing
disk records for whatever reason.
Could you open a ticket on our bug tracker at
https://trac.torproject.org with steps to reproduce what you have
encountered?