i know this may appear picky and have no desire to offend.

but technically the bishop is the pastor of the entire diocese and of each church.

perhaps in imitation of the protestant practice the church in the usa came to call the ordained head of the parish pastor. the language of church law calls such a priest " parish priest" parochus.

since the issue at hand is church titles , hope this observation is to the point.
also it is worth observing that the american church has unique practices.

we are out of step with most of the church in this area of clerical addresses and historically our use of the title father for secular priests is an anomaly