

That’s the case in any country with high speed rail: tracks are the devils of the details.
I mean in the end, especially with a country as small as France, there’s not a whole lot of difference between 320 and 350km/h. (I mean going one end of China to the other and that difference adds up, but not one end of France to the other.)
But … what’s stopping them from making the track changes needed?
Endemic everywhere I’ve used HSR. It’s a pity, really. (Though at least some of them will provide a luggage car that you can put larger or higher-count luggage in.)