Unfortunately, that IRCAM article is essentially a brief retelling of the standard "history" of electroacoustic music that leaves out predecessors like Cage and Ruttmann. Indeed, it leaves out the whole context for Schaeffer and his work, so nothing about electronic instruments or the sound on film technology that people were using in the thirties. I think that isolating Schaeffer like this (not even mentioning his colleague Pierre Henry or their contemporary (who possibly preceded them in his work with wire recording) Francis Dhomont) obscures his real and lasting contributions to music, all in the service of making him out to be "the first."
Fact is, Schaeffer was a significant figure in a long line of musical exploration. The article, to be fair, does suggest this, but without any names--Schwitters, El-Dabh, even Hindemith and Toch--the rather subtle "One source of..." which introduces Schaeffer doesn't really even suggest the wide-ranging activities that preceded "musique concrète, activities that included technique as well as philosophy. The idea of musique concrète, after all, is already present in the experiments of Toch and Hindemith, in concerts by the Futurists, in pieces for variable speed turntables as well as for common, household items by John Cage. I think that ultimately, that presentation of Schaeffer as "the" pioneer serves to diminish his actual contributions, which were enormous and which continue to this day.