Нет, "наместник Божий" - это именно что офиц. титул папы, vicarius Cristi. Ни у английского, ни у датского монархов, хотя они возглавляют свои церкви, такого титула нет, потому что он епископский, т.е. относящийся к апостольскому преемству.
А почему ты считаешь, что vicarius Cristi = наместник божий?? Вообще-то это Викарий Христа (
https://ru.wikipedia.org/wiki/Титул_папы_римского)
Да и с этим наместником\викарием Христа не все так просто:
Vicar of Jesus Christ
"Vicar of Jesus Christ" (Vicarius Iesu Christi) is one of the official titles of the Pope given in the Annuario Pontificio. It is commonly used in the slightly abbreviated form "Vicar of Christ" (Vicarius Christi). While it is only one of the terms with which the Pope is referred to as "Vicar", it is "more expressive of his supreme headship of the Church on earth, which he bears in virtue of the commission of Christ and with vicarial power derived from him", a vicarial power believed to have been conferred on Saint Peter when Christ said to him: "Feed my lambs...Feed my sheep" (John 21:16-17).[104]
The first record of the application of this title to a Bishop of Rome appears in a synod of 495 with reference to Pope Gelasius I.[105] But at that time, and down to the 9th century, other bishops too referred to themselves as vicars of Christ, and for another four centuries this description was sometimes used of kings and even judges,[106] as it had been used in the 5th and 6th centuries to refer to the Byzantine emperor.[107] Earlier still, in the 3rd century, Tertullian used "vicar of Christ" to refer to the Holy Spirit[108][109] sent by Jesus.[110] Its use specifically for the Pope appears in the 13th century in connection with the reforms of Pope Innocent III,[107] as can be observed already in his 1199 letter to Leo I, King of Armenia.[111] Other historians suggest that this title was already used in this way in association with the pontificate of Pope Eugene III (1145–1153).[105]
This title "Vicar of Christ" is thus not used of the Pope alone and has been used of all bishops since the early centuries.[112] The Second Vatican Council referred to all bishops as "vicars and ambassadors of Christ",[113] and this description of the bishops was repeated by Pope John Paul II in his encyclical Ut unum sint, 95. The difference is that the other bishops are vicars of Christ for their own local churches, the Pope is vicar of Christ for the whole Church.[114]
On at least one occasion the title "Vicar of God" (a reference to Christ as God) was used of the pope.[104]
The title "Vicar of Peter" (Vicarius Petri) is used only of the Pope, not of other bishops. Variations of it include: "Vicar of the Prince of the Apostles" (Vicarius Principis Apostolorum) and "Vicar of the Apostolic See" (Vicarius Sedis Apostolicae).[104] Saint Boniface described Pope Gregory II as vicar of Peter in the oath of fealty that he took in 722.[115] In today's Roman Missal, the description "vicar of Peter" is found also in the collect of the Mass for a saint who was a pope.[116]
https://en.wikipedia.org/wiki/Pope#V...f_Jesus_Christ
Как видим, викарием Христа кого только не называли, вплоть до королей и судей. Обрати внимание на эту строчку:
On at least one occasion the title "Vicar of God" (a reference to Christ as God) was used of the pope.[104]
Это уже явно ближе к нашему термину наместник божий. И это явно не официальный титул, а достаточно редкое словосочетание за пределами русской культуры. Так что, нет, наместник божий - это не какой-то однозначный титул. Это просто в русской культуре так называли папу римского, как главу христианства. Да и не только. Вот по гуглу пробивается, что наместниками божьими вообще даже архангелов называли:
https://ru.wikipedia.org/wiki/Филон_Александрийский
Так что не вижу причин, по какой я не могу назвать наместниками божьими глав других церквей с их т.зр. Это словосочетание не 100% четкий юридический и\или документальный термин.