The way Giggle translates the text, I doubt they really went supersonic, they were just to test the wings for a supersonic a/c….
The study supersonic glider Arsenal 1301, 1950.
Two gliders are made in size in 1949, ARS 1301 wing triangular thin profile and the LRA 2301 in-wing thin profile with a very high spire. Towed by the NC "Martinet," the "Languedoc" or a DC-3, tests of these machines is carried out in 1950, providing engineers with much information, a release was made May 24, 1951. A prototype supersonic fighter delta wing is commended to the Arsenal of the aircraft beginning in 1952. This project will lead to the North Interceptor 1400 "Gerfaut" and Nord 1500 "Griffon".