No, it's not true, but I can see how the deist fellow might get that idea.
Laws against discrimination on the basis of religion extend to cover atheists. That's not because atheism is officially a religion, but because there are additional clauses in the laws to include those with no religion.
If atheism really were classified as a religion, atheist organisations could apply for the same tax exemptions as churches. As it is, the best they can do is get recognised as non-profit charities, like the secular Red Cross.