OK... let's change the emphasis from "you must tell ATC" and "what's the point, we never can aim for 160 to 4".
Airbus A319/320/321 into LHR we are invariably told "160 to 4". In practice I fly 160, Flap 2, Gear up to the minimum SOP height of 1600'. I then tell it to fly Final Approach speed (which it will take no notice of because 160K F2 and 3deg slope is essentially idle), and Gear Down - which after a few seconds does start the speed coming back. Remaining Flap
not used as speedbrake, but taken as required, and prior to 1000' to keep the spy in the cab happy
At 4D the speed is probably ~150K reducing slowly, maybe a little more. From watching my P2 colleagues, I leave it a little later than most, with either the 1600' being "anticipated" or the Flaps used as speedbrake, hence earlier / more rapid speed reduction and earlier spool up.
So LHR ATCOs, are the BA Airbuses causing you regular problems? Or just the odd one? As I said above, I can almost 100% guarantee no BA Airbus aims to fly 160 to 4... If you really want us to admit that on every approach, we can, but you seem to cope pretty well with us not doing so for the last X years! 757 was the same - slowed from 160K at 5NM.