Importing is determined by the group and field keys. If there are no duplicates then there should not be a problem.
Field groups where the field group key already exists are ignored, so you can’t “Sync” groups this way.
You will have an issue where the group key is unique and there is a field key that is the same as a field key in an existing group. I’m not sure about what issues this will call, but both fields will exist which will cause problems getting, setting and using these fields. This should be avoided.
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