No ship in Elite should be able to fly Backwards, faster than any ship can fly Forwards.
And that is certainly currently possible.
Reverse thrust should be capped at 50 - 100/sec.
Dunno where the cap for large ships currently is if you fly with four pips on eng backwards.
But flying backwards with FAoff is a bit of a different matter since you use your mainthrusters to accelerate and then turn the ship around.