If you use the passageway then you don't need to reclear security, but otherwise it seems a rather pointless conversation: if you know it's easy to walk from B to A then you don't need to discuss it. If you are unsure about this, then yes, have the conversation and indeed it probably isn't recommended for the unsure, the uncertain or those who like to keep their ducks in a row. Every so often someone does manage to get horribly lost in T5 so I can see where the staff member was coming from.

Not clear who you were talking to, if it was someone who predominantly spent their working life landside I can see they would perhaps not be familiar with it.