Thanks for reporting the issue. The problem was actually in the bbpnns plugin. Future publishing calls the
save_post action, which is actually supported by bbpnns, but was expecting $_POST to be set to determine whether to send out notifications. The future publishing action does not set $_POST, so the default setting of whether to send notifications on saving posts needs to be taken into consideration.
I’ve released the fix in bbpnns v1.17, but you’ll have to make sure to tick the checkbox to send notifications on save under Settings > Forums > Email Notifications.