No, actually it is saying that every governor since 1882 (except, by implication of “yet”, the current one implied to exist) is also dead, not just that the 1882 governor is dead. Of course, in the limit case if there were no governors after 1882 (except the current one, if any) it would just say the one in 1882 was dead, but there were, in fact, 24 or 25, depending on exactly when in 1882 the tortoise arrived (not sure on that), subsequent governors before the position was abolished with home rule which quickly transitioned into independence.

Which makes the “yet” weird, but I suppose it admits the possibility that the office might be restored before the tortoise dies, and the tortoise might not outlive the potential future governor.