Outer plates get thinner and thinner, as the number of "speeds" increases. That means the marked part in the picture is thinner for 10, 11, 12 than it is for 7, or 8 speed chains. Some manufacturers recommend not re-using quick links with 10+ speed chains, probably because the safety margin is lower with such thin outer plates. My guess (and experience) is that, like others have said, with some common sense, even 10+ speed quick links can be reused as long as they lock securely (not too easily).
... although, common sense also tells me there's no need to go with more than 8 speeds unless racing.