Reading the letter carefully, one observes the following:
It was a governmental decision to allow only the vaccinated, and the only comment in the letter about that decision is an observation that the government's decision has been "generally well-received by the faithful."
The mandate to the Church leadership is to ensure WHO protocols are strictly adhered to, NOT that the government's decision is adhered to.
Reading between the lines, I think the Archbishop is telling everyone that if they will happily go along with the charade, everyone can still attend Mass, in spite of the government's decision (except for the priests themselves, who, the Archbishop explicitly states, must be vaccinated).
"Behold, I send you forth as sheep in the midst of wolves: be ye therefore wise as serpents, and harmless as doves."

this bishop is a serf