Well, No.
The events contributor can only edit events. Where the WP manage_categories capability includes Post Tags, it would make sense for the manage_events_categories to include Event Tags (but not post tags).
If the manage_categories capability is added, the user can also edit Post Tags which is undesirable.
The really strange part is that the Events Tags metabox is displayed if manage_events_categories is permitted but the box is empty which suggests that it should be populated but something prevents it.
Thank You for the response. As soon as I (re)built the index it worked great. I’m really impressed with the plugin overall. It provides granular control and great functionality.
Great work!