I guess the wording doesn't technically ban you from displaying historical platform information, but that would likely be a bad-faith use of the data anyway...
[1] http://www.nationalrail.co.uk/static/documents/Terms_and_Con...
[2] http://www.nationalrail.co.uk/static/documents/Developer_Gui... "Occasionally Time-Bound Data will become available through NRE feeds before it is ready to be published to the public. [...] One such example of Time-Bound Data is platform numbers. Early display of platform numbers, particularly at origin and destination stations, can lead to platform overcrowding and/or staff not having sufficient time to prepare the train for oncoming passengers. In some instances, platform numbers will be available in Darwin before being displayed on screens in stations."