Hawaii’s electoral votes were never changed. They submitted slates of electors for BOTH candidates. It was the final result of the state’s popular vote that changed from one candidate to another after the electoral vote deadline, not the certified electoral vote.
Something worth noting here is that Congress could have legitimately voted to accept the Nixon electors from Hawaii even though the final popular vote totals published in late December 1960 showed Kennedy as the winner. That’s the risk a state runs when it can’t get its act together in the electoral vote process. There’s no guarantee that Congress will get it “right.”
The Governor submitted them for Nixon, which was changed at a later date. December 14th wasn’t the final date. The state has the final say.