What i mean by"never differentiated between bishops and elders" was that of referring to two ordained pastoral offices, which i think you concur with me on. And that there was no class of clergy distinctively titled "hiereus"="priest."
I believe the elders were basically the ones who were aged or had been long with the Christian knowledge.
There is no disagreement there, as Titus was to ordain mature qualified men, presbuteros (senior/elder), but he was to ordain such as elders in the formal sense, who are also called episkopos (superintendent/overseer).
Both Timothy and Titus were to pick elders and to appoint them to the position of Bishops and deacons.
Rather, the text you cited, Titus 1:5-7, uses presbuteros (senior/elder) and episkopos (superintendent/overseer) interchangeably, instructing pastor Titus to appoint presbuteros and thus telling him what the qualifications of a episkopos were to be.
Presbuteros likely is used to refer to the character of the person as a mature person, while episkopos refers to his function.
Also see,
And from Miletus he sent to Ephesus, and called the elders of the church. (Acts 20:17)
Take heed therefore unto yourselves, and to all the flock, over the which the Holy Ghost hath made you overseers, to feed the church of God, which he hath purchased with his own blood. (Acts 20:28)
And from Miletus he sent to Ephesus, and called the elders of the church. (Acts 20:17)
The bishops and deacons were still elders but the elders were not necessarily bishops and deacons.