FWIW where I am at present the F/O's are taught they MUST override the expected landing weight and set that Vref speed.
On occasion I point out to them, on final approach, that the FMC approach speed is actually 1 kt FASTER than the Vref they set due track shortening, damned fine efficient descent profile....whatever.
No hassles, just reselect the correct approach speed.
After landing I just discuss what would happen IF an accident occurred and in evidence it was found the crew were KNOWINGLY using an incorrect Vref setting for the actual landing weight??
Suppose whether the argument from the prosecution or defence in the courtroom!
Cheers.