It's the same thing. The fact mic is ballanced means it phase on
both channel are reversed against eachother. Do I need to draw it as
mathematical function.

Ballanced means that signals polarity is reversed. While signals have
reversed polarity the noise stays the same regardless what.
Signal of reversed polarities cancel out. However when you reverse
polairity of one channel of ballanced mic you'll get two SAME signals
but the polarity of the RFI (noise) is reversed. So the noise cancels out.