I know this is a bit of an older post, but since nobody else has replied, I'm going to give it a shot. Harmonize is a 3rd party app that's integrated with Canvas, not something Instructure themselves. Because of that, I'd highly recommend reaching out to Harmonize Support about this issue, as they would be the ones that would need to change the way they integrate with Canvas (or provide you with options) so that calendar items wouldn't be created.
I hope this info helps a bit. I'm going to mark this as the "solution" to your question, which really just means that someone has provided an answer. You can feel free to unmark this as a solution and reply here if you'd like though!