This is no longer the case - the last API update removes this restriction.
CanSendNotifications property is still valid for cases when the agent itself won't be able to send notifications from other reasons and you should still check that.
We will add in the next release a way of setting that notification so that it's not allowing duplicates like:
public bool SendNotificationToAllDevices(string message, NotificationPriority priority, bool allowMultipleNotifications = false)
However, CanSendNotifications will still return true unless the agent itself is not allowed to send any notifications.