This is an exaggeration, for although it was a major first step towards Cubism it is not yet Cubist. The disruptive, expressionist element in it is even contrary to the spirit of Cubism, which looked at the world in a detached, realistic spirit.
Is it true that the first Cubist picture is The Demoiselles? 
although it was a major first step towards Cubism it is not yet Cubist.