I've not been to Liphook for a long time, are the platforms unusually low? They are straight so there shouldn't be much of a gap. As Horizon22 has pointed out, there is little chance of someone requiring a ramp to board the train reaching the down platform anyway.The notice itself is a bit clearer:
Which based on the rest of the article I think basically means there's no practical way for them to deploy a ramp on the platform - presumably the combination of narrow platforms and relatively tall gap means that a ramp deployed would either be too steep or would block the platform/leave too little 'landing space' when deployed