You need to search the code on the site. More than likely there is a filter that is automatically adding the rows when the repeater value is loaded. It could be on the hooks acf/load_value. acf/load_field or acf/prepare_field. There might be others. This is the only way that rows could be automatically added when the repeater field settings does not have a minimum number of rows. I would search the theme for all ACF hooks to see what I could find, but I can’t really tell you exactly what to search for.
The previous developer must have had a reason for doing this. I would also be looking at the code to figure out why. Removing them might cause errors depending on how it is coded.
