I have been experiencing the same problem. Not using iCloud and I have never once seen a merge conflict notification either. It doesn’t happen enough to usually be a concern but it removed text that I had added to a file and had to restore from a version history copy.
My workflow is desktop open most of the day and then use the iPhone app randomly throughout the day. To avoid sync errors I had been waiting for sync to finish on the iPhone before I make any adjustments but it still randomly happens.