It does set them apart in function, because the functions are priestly: annointing, for example (James 5:14) has no other significance but as a sacrament; πρεσβυτεροι are shown to be sacramentally ordained, therefore also separate formally (Titus 1:5) and through the ordainment receiving a particular grace (1 Timothy 4:14), and have privileges (1 Timothy 5:19), whether similar to OT elders or not. I am adressing the only substantive point in your recent post that I could see.
when they are different in meaning
Here you need to widen your horizon beyond English. Of course, English "priest" can also mean a voodoo shaman, or a Hebrew "ιερευς", but specifically "πρεσβυτερος" in the Titus and the Timothys has been shown to refer to functionally distinct nascent from of church service and so has taken on the new meaning of Catholic (or generally Christian) priest. The etymology of "priest" is clearly "πρεσβυτερος", but in English "priest" has more meanings than "πρεσβυτερος" has in Greek. And, I hasten to add, the New Testament "πρεσβυτερος" has meanings other than "priest" outside of the Titus and the Timothys, and that other meaning should be translated as "elder" or something similar, -- no one has argued otherwise.
It is usually a good idea to understand the linguistic argument before wading into it. Especially, understand that unless you are translating between two closely related languages, e.g. from Italian to Spanish, you will not have a 1-1 correspondence of most words, and 1-1 correspondence between "priest" and "πρεσβυτερος" has not been alleged. It only is such in Titus and Timothys, where the topic of apostolic succession is covered by St. Paul, and new use of the word "πρεσβυτερος" is introduced.
Did God really say?
Besides ignoring what i said about these attempts (Ja. 5:1, etc.), while you are reduced to arguing for formally entitling πρεσβύτερος/presbuteros as ἱερεύς/hiereus due to some priestly functions, they are distinct because the NT pastors are not engaging in making expiatory sacrifices as a separate priesthood, despite Rome's assertions otherwise, and thus the Holy Spirit makes the distinction which Rome ignores by never referring to NT pastors by the unique title for priest.
Here you need to widen your horizon beyond English...has taken on the new meaning of Catholic..
Meaning to fit a later developed job description. It is who am going by the linguistics of the Scriptures, while Rome supposes she can subject Scripture to fit her doctrine. It is due to Rome's Eucharistic theology that the distinguishing title was given. A "new type of service" indeed. You are basically lecturing the Holy Spirit, reproving Him for not once giving the titled hiereus to the NT pastors in distinction from all believers, for how could He fail to see that they were distinctly like expiatory Jewish priests of Rome? And that they also really are supposed to be celibate. Rome is so arrogantly helpful.
I am weary of your sophistry. Your laborious vain attempts to justify doing what the Holy Spirit never once did simply testifies to the incredulity that defenders of Rome must often go to due to defend her traditions from Scripture. But which at least proves that she did not rewrite the Scriptures, as the Muslims are reduced to arguing.