Mary, that is “very” interesting as it might also answer a problem I’m having with something totally unrelated but similar. I duplicated the behavior on my own instance, but mine is Project Pro for O365 so I’m getting the most current bits. I have access to another machine that has an earlier version of 2013 and will let you know if I find something different. You are correct that using my Project 2010 version I’m getting the behavior you were originally expecting.
I would like to do some additional research to see what might be the root cause of both of our concerns. This may take some time but I will reply if and when I find anything. Just in case, if you don’t hear anything within the next few weeks and nobody else has responded with a better answer then feel free to post a reply and I’ll get it.