Each catalog master template has at least 7 variants, so that they can fit in products of varying dimensions without cropping or distorting them.
When you customize a template variation then the entire family (edited and unedited variations) is shifted to this personal library.
You will have to replicate the edits across variations if you want them reflected in ALL your creatives.
You can do that by following these steps while editing your template:
1. On the Review & Save screen, choose Master Template and click on Edit under any variation.
2. After you have made the changes, click on the other variation (left panel).
2. Continue editing other variations.
3. Click Done once you've finished.
The system will update your My Template.