I couldn't get to the article because it's a pay site. However I never said drugs didn't come in other ways, and the title of the article seems to indicate all our borders, not just the south.
The easiest and safest way to get drugs across our southern border is to simply walk across. However even that presents some kind of risk, so now they are using drones to get the drugs across. If they bust a drone, nobody ends up in prison. They just lose a lot of money. Right now that's the problem they are trying to find a cure for.
People using vehicles to get drugs across are taking a huge risk because of dogs. Dogs can sniff out drugs from anywhere. I've never seen it myself, but I understand they have a dock by the border just in case they need to unload it for inspection, and they will.
The profit margin and size of the market make it impossible to stop the flow of drugs or even seriously reduce the supply at our borders. If you build a higher wall the cartels will use longer ladders. If you dig a deeper base, they will dig deeper tunnels. And if you build an impenetrable barrier, they will just go around it.
The answer to reducing the drug trade is not by building taller barriers , but working on both sides of the border to reduce both demand and supply.