This actually appears to be the normal, I found a trailer strip I have and it is the same way. (image cropped from a longer strip)
Also a pic of leader strip I used to have.
Both have the different perfs from the stamp and the attached strips.
The attached strips are a different perf gauge all together, the stamp is perf 10 and the trailer strip is perf 12-1/2.
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Large and small hole perfs both have the same gauge, it is just that the size of the holes and spacing between them are slightly different.
The top stamps are the large hole, bottom small hole.
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Edit added (image cropped from a longer strip)