There are no Proof 1967 Kennedy Half Dollars. The only special treatment they received was for the Special Mint Sets, which are not considered to be Proof coins, although some of them are very close to Proof status.
1967 would have been a special mint set, so the proof destination wouldn't apply if I'm not mistaken?
There were no proofs produced by the mint between 1965 and 1967. While some SMS coins from early die states are nearly proof-like, none are actually proofs. So no mistake. Some graders will grade coins that got some sort of special processing by the mint using "SP" grades or something similar.