So, time to clear things up here.
1) Greyhaus IS open to submissions! You can see the submission guidelines below.
2) Greyhaus does acquire both single title and series romance. Please make sure you know what you write. I would really stress this is especially true for the series lines. If you do not know the guidelines for Harlequin, please take the time to review those.
3) As I said, I am looking at both single title and Harlequin. I just happen to be on a big push to acquire authors in each of the Harlequin lines.