Sorry, I don’t know the answer. The Holy Trinity is God the Father, God the Son, and God the Holy Spirit in one God. Jesus said that blasphemy against God the Father and Himself would be forgiven, but not the Holy Spirit. There must be a reason for the distinction when the Holy Spirit is a person of one God. An answer on the church’s teachings is found in the link I posted earlier:
Edit: Perhaps Jesus spoke it this way to again emphasize the mystery of the Holy Trinity?