Gene,
It might be. The Manufrance building remains on Rue de la Convention, in St. Etienne, with the chamber of commerce building next to it, and the Darne works across the side street. The old Manufrance building stretches for more than a few blocks, and is enormous.
But, it has been divided up into retail space and shops. It had been out of business for some time when I was there, and I didn't seek out information on those guns.

Geoffroy speaks English as a third language, behind French and Waloon, and I have a bit of trouble communicating with him, and noticed much the same on his website. If you speak French as well as you write it, you could ask him yourself. He responds to email pretty much daily, in my experience.
If the folks on your French blogs are based in St. Etienne, they may well have been employed in the gun trade, or, moonlighted in it, and would have a depth of knowledge we here could never approach. At one time, a big percentage of the population in that town made their living, or part of it, in the gun trade.
As I have pointed out, Manufrance guns were not something I was, or, am, interested in. I'm sure they are superb guns. A friend owns an Ideal, a Costo and a Robust, nobody can hit anything with the Ideal, and the other two have been rode hard and put up wet, in addition to being hard to hit anything with. All three have pretty significant pitting in the barrels, not uncommon on old French guns, but, I've moved on from my pitted barrels phase. I was distracted enough with the Darnes, I guess.
Good luck.

Best,
Ted