Very good point, the thickness could be an issue. Hadn’t thought of that but when I read the CWC website again:
Please note, the 18mm can be a tight fit when used on certain years of the G10 range of watches, but they do go on. Inserting the end sideways can help thread it through the gap, and a side-to-side motion as you work it through also helps. If you are unable to get it through, you can use a small vice or pliers (with a cloth over the end of the strap to keep it clean), compress the end and work it side-to-side to pull it through.