PTGRail explains the purpose of 'flashing' signal aspects (and how to approach them whilst driving) really well in his British Signalling Guide video for TSC (this also applies to UK routes in TSW): (from 16:15 to 18:21) Hope this helps explain what 'flashing' aspects mean .
They were in preparation for 140mph running which never happened. Rather than revert them, they were just left that way and are to be treated as normal.