French bikes probably handle differently than Brit/US/Italian bikes because the french used tubing in metric diameters. So where the "standard" top tube is 1 inch O.D. (25.4 mm) the comparable french tube is 26 mm. It's not a lot of difference but maybe enough to contribute to handling characteristics differences.
And we all know how difficult is is to install campagnolo top tube brake cable clips around a french tubed bike. It much more satisfying to find and install a set of simplex clips on a french top tube.
I think it is reasonable to assert that mountain bike needs lead to some important experimentation and the re-discovery that you can make a lighter stronger frame by increasing the diameter of the tubes. It is fundamental mechanics theory but long overlooked/ignored/unknown by the craftsman builders.
Todd Teachout
Hercules, CA