Hello Gabe,
What you've described is not what is supposed to be happening. After a lengthy review of the current logic in the code, we think we may have found a case where the email notification is not happening when the only thing changed was the "shared with" value. If anything else was changed, such as the date / time / venue, then the proper notifications would have been sent. We'll make an adjustment to the code to hopefully fix this issue later today, so if you notice this is still happening after tomorrow, please let us know.
Thanks for pointing out this issue to us.
Shaun