I do not know about undergrad applicants, but I feel that it is probably ok.
As a grad student, Dr. Kasberg really likes communication. Updates in your application are good or an update to see how your application is being processed is fine as well. They do not like emailing them after you have had your interview though (in terms of updates on their decision).
Yes, this happened to my friend last year, so she will be starting this upcoming July. In her case, she did not put that she was pursuing her master's and they told her that they would be able to accept her after she graduated with her master's (which is this summer). I also have another friend that is D22 right now and interviewed 2 cycles ago. She was told that she had a deferred acceptance and would need to get her master's in a year before starting. I do not know why they do this, but it happens with every cycle. I believe they will let you know what the conditions are of your deferred acceptance and it will only make you a better dental student 🙂