All the Group Standards are freely available at www.rgsonline.co.uk and this confirms 0045 issue 3 is current.
I don't know the layout at Hertford, but is this a location where red lights could cause confusion etc as per the clause quoted?
They say it is due to the read across but its been fine for the past 30odd years with no incidents or reported confusion.
Its just network rail fixing what isn't broken.