I’m not so sure. In a union position one must have a documented set of occurrences. The 2 year cycle could simply have been to document the issue so he could be dismissed.
I had this at work recently. An employee was being called into HR for missing (calling in sick) 14 days in three months. That comes to 14 "occurances", and you are fired after 5. The supervisor was keel hauled for making it into an issue for not doing his job times three.