TFL did attempt a trial on the DLR which at the time didnt have a before door "hustle alarm":
TFL DLR Testing
Was an intresting read, more so pages 13 onwards for me
That TfL report (of 2018) is interesting and relevant- thank you. The RAIB report on the Ealing Broadway incident make no reference to it, nor to the Docklands Light Railway (DLR) at all, and only seven uses of the words 'hustle alarm'. Although the RAIB report refers to the possibility of behavioural issues, the TFL report of several years previous, shows clearly that 'door closure warning sounds' are associated with passengers hurrying, causing problems and delays, indeed on one two-day trial there were 12 incidents of passengers trapped in closing doors.
The TFL trials suggest strongly that hustle alarms contribute to increased safety-related incidents. They also contributed to increased staff tiredness and thus also reducing attentiveness and increased safety risks.
The TfL report also refers to studies carried out previously on the London Underground, though I did not see any specific mention of findings. Perhaps these informed the 'three second audible alarm' required to 'assist' disabled persons by The Rail Vehicle Accessibility Regulations 2010 (RVAR).
I hesitate to reiterate that the train involved at Ealing Broadway was the 'last train' (so passengers less likely to 'stand back'), and the driver had 'previous' regarding competence (RAIB report para 128 et seq).
The TfL study appears to suggest that the RVAR requirements should also be reviewed; this too is not referred to in the RAIB report, perhaps because no-one involved is reported as having any impairment.