Alas if Pathe had issued transcriptions of the dead Rudolf Steiner I think it would have been well publicised, sorry to dash any hopes :-(
As nobody seems to have heard of him, and there does not seem to be any press notices, it may of course be a pseudonym for another artist in the Pathe stable trying out other repertoire? A wild suggestion but possible.
There is another disc recorded by 'Rudolf Steiner' on Pathe X93025 that is mentioned in the Gramophone Shop Encyclopaedia of 1936.
Grieg: Jeg elsker dig (Ich liebe dich), op. 5, no. 3
Grechaninov: O my country, op. 1, no. 4
Still don't know who he was but the catalogue numbers do indicate a recording date for the second half of 1931.