I've seen this in Brittany too.
It's a standard of confusing direction signing that is only reached in Britain when West Sussex County Council are given the job. But that's another rant.
That may be because the British have an inherent distaste for the concept of toll roads and work on the principle that "I've paid my road tax and I'm therefore ENTITLED to sit in a queue at Spaghetti Junction, rather than pay for the privilege of by-passing it quickly".
The difference between French traffic congestion and English traffic congestion is that the French provide a déviation and the English provide a diversion.