Repeating events are the ones a calendar gets wrong quietly. The original series copies across correctly, and then someone changes it — the weekly call moves an hour later, a date gets skipped, the whole thing shifts when the organiser changes timezone — and the copies carry on describing the old arrangement. Nothing errors, so nothing tells you the two calendars stopped agreeing.
Changes to a series now reach the copies. Editing the repeat rule updates them, skipping a single date removes that occurrence rather than leaving it stranded, and moving the series to another timezone moves every occurrence with it rather than shifting the first and leaving the rest behind.
Single occurrences are handled as their own thing. Moving next Tuesday's instance of a weekly meeting changes next Tuesday, and the rest of the series stays where it is — which is what the original calendar does, and therefore what the copy should do.
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