If she really wanted to stay anonymous, she would have chosen a different publisher, publicist, agent, etc.
At least one editor has already admitted to passing on the book, not knowing Rowling wrote it, so she went through the "normal" means of querying under the pen name, not saying "I'm JK Rowling, and I want to publish under a pseudonym"
I will say though, it will look fishier if the Lawyer who leaked the information isn't reprimanded or fired, since he broke client confidentiality.
If she openly released the book with her name attached, it would instantly be compared to her past successes and receive false praise or scrutiny based on her achievements as a fantasy writer.