Nonobjectivity of Malevich's and wordlilessness of Reinhardt's black square

The similarity between Ad Reinhardt's "black" paintings and Malevich's Black square on a white field is plain, even though Reinhardt considered Mondrian rather than Malevich the key reference for his abstract painting. Similarity surpasses mere form, a shape of a square of black colour, for it also exists in the abundance of verbal explanation, justification of the act of nullifying and of negation, which is represented or performed by a black square in Malevich's and Reinhardt's art respectively. What does, then, Malevich's appeal to "nonobjectivity", to overcoming of the nature (the world as we know it) with art on the one hand, and Reinhardt's swearing on the autonomy of art, on the exorcising the nature and the world from art, the swearing on the art's "wordlilessness", on the other hand, mean?