From what i have seen, this is common among 10 round reduced capacity magazines. The manufactures are more concerned that you will not be able to load more than 10 rounds then they are concerned that you will be able to easily load the 10th round.
I am unclear why one would buy reduced capacity magazines just in cases the laws change. Even in California, owners of magazines that held more than 10 rounds had their mags grandfathered when the laws changed. In other words, while magazines purchased new could not hold more than 10 rounds, those that already owned mags that could hold more than 10 rounds were legally able to keep and use them. Maybe i am missing something.