This isn't designed to stop attackers with physical access. This is designed to stop casual tinkerers and shade tree mechanics.
You know what isn't vulnerable? A "dumb" offline charger. You know what doesn't make any money or turn the consumer into another product? A "dumb" offline charger.
If it were about physical security, the suggested fix would be to remove the communication from the port entirely.
Companies shouldn't get to make something simple and secure into something inherently insecure and then iterate security into it. Like drive by wire steering, or brakes. Nobody asked for these things and if you ask ANYONE who works on, builds, or actually enjoys cars the consensus is NOBODY wants it.
But there are enough sophomoric, pedestrian car owners out there who gawk at the senseless overdeployment of technology and think "this is so convinient" and don't see it as 1) regulatory barrier building and gatekeeping 2) enabling vendor lock in 3) overcoming right to repair legislation. So the knowledgeable and enthusiastic voices of reason who care about cars get drowned out by the hoard of pedestrian geeks who couldn't imagine operating a car without at least a 16 inch touchscreen.
In security, the best defense is not introducing a vulnerability at all. There is value in having less code. For example, if your PaaS doesn't collect user SSNs... then it can't lose SSNs in a breach.
The question here should not be "why is this not secure." The question should be "why does this even need to be secure in the first place?" We have a very simple task to do and we've complicated it so much we've introduced vulnerability that didn't exist previously.