I hate to contest your otherwise excelllent knowledge of all things Luton LTNman but I have checked on this and the above mentioned tragedy in 2009 was what prompted the H&SE site inspection which led to an instruction to "to segregate pedestrians and vehicles" - of which the result was the installation of the pavement railings.
I will dig deeper but I think you are wrong. I think the investigation found that the pedestrian crossing was badly positioned and had to be moved. The crossing remained but in a slightly different location so at the crossing point there was obviously still no segregation. I will see what I can find out about the railing history.