The channel's open to anyone who wants to post an event. Many events aren't relevant to each individual because of subject matter, domain, location or as in this situation, leadership level. So it's hard to filter in this manner on Slack. It's probably good practice for people posting events to list the qualifiers up front, but trying to create a separate Slack channel may not solve this topic. I like the idea of an open channel for executive type leaders. But generally people are looking for events in the events channel.
Feel free to reach out to me directly if you have additional concerns or ideas.