I bought a platform ticket at Leeds today to meet my wife off her train. At the gateline I was asked which platform I was going to. I asked why it mattered and was told they check this with platform tickets. I've never come across this before, including at Leeds, and indeed it seems a pointless challenge as, not only does the ticket allow the holder to visit multiple platforms, if anyone was so minded they could simply name any random platform. Has anyone else encountered this?