I have travelled extensively for many years and can only remember once or possibly twice being asked to show a bag tag as proof that it was my baggage.
The potential downside to going through customs with someone else's bag is far greater than the potential upside, you would have to pretty stupid to try this unless you targeted a specific bag knowing that something of value was in it.
I think the original post is either made up or the poster has a vivid imagination.
I once picked up a bag at CPT after an international flight and went home with it, only when I tried to open the case, identical with mine, and realising that the combination on the lock was not correct, did I see it wasn't mine. I managed to open it and definitely not mine, wrong size knickers and bras for a start, but found a book with a name and address not far from my house, got the phone number, called, and a very distressed sounding lady said : "Oh my daughter has just got back from overseas and she has somebody else's suitcase ......" So that had a happy ending (not in the massage parlour sense though!).