Actually, most schools have some reuirements for math. But I really do not think accounting phd's use of math is that complicated if you focus on empirical work.
it depends on the school you are applying for. Some schools, such as stanford , are very demanding of math. But overall, I think the requirement of math for accounting PhD is not as high as for some other hDs, such as Finance PhD concentrated in asset pricing.
Some schools do state that they have high requirement for math. But requirement is not a necessary condition to be a good accounting scholar. Do you really think Mary Barth's accounting standard and value relevance research need math?