I don't know much about Accounting PhD. But I've been in a couple courses at the Department of Economics with two Accounting PhD students. And we had to do a lot of math, we all found it very difficult, and struggled a lot with everything. Well, even the professors often had trouble, and sometimes were unable to answer some questions or solve some problems. If that's important for their research, I don't know. But they were taking more courses over there than I did, so I guess it's important.