Shouldn't the authors of all articles in a magazine be given in the light of 2 Tim.3:14 “..knowing of whom thou hast learnt [them]”? Otherwise one could be reading writers who are in error as to the truth.
The questioner only quotes part of 2 Tim. 3: 14, 15. It goes on to say “and that from a child thou hast known the sacred letters..,”. There are thus two sources given to provide certainty and confidence for Timothy: One is what I will call accredited ministry, “knowing of whom thou hast learnt [them]”; the other is the OT Scriptures, “the sacred letters”.
When Paul wrote to Timothy, the Scriptures were incomplete, the NT was unfinished. The OT was complete and available but even the NT books that had been written were not generally available. Where were the truths of Christianity to be learnt? Not in the OT, for what was distinctive to Christianity was not there. God had chosen vessels, generally the apostles and NT prophets. to whom He communicated directly the doctrines of Christianity (See Eph.3: 3). They had direct revelation from God and the divinely given authority for its promulgation. The revelations they had came not from the OT Scriptures, nor through any other channel, but direct and immediately from God. Paul was the great example of this and God testified to it with peculiar signs (2 Cor. 12: 12). These distinctive signs authenticated or accredited what they promulgated. The apostles and prophets were distinct and were the foundation of the assembly (Eph. 2: 20). Foundations are laid only once, and then when the building starts to rise they disappear. The apostles and prophets have gone, their work is complete, there are no apostles and prophets today. Such ministry Timothy could rely on knowing of whom he had learnt these things. It was also in keeping with previous revelations in the OT providing a second source of confidence (Acts 17: 11).
The situation when Paul wrote to Timothy is not what we have today. The apostles and prophets have gone, but not before the NT, and hence the Scriptures in their entirety, were completed. What God revealed to those accredited ministers is now enshrined permanently in the N.T. Scriptures. Paul completed the word of God in the sense of the subject matter (Col. 1: 25), John did so historically, as his were the last writings in time. Thus now there is only one authoritative source, the Bible. In a word then, what the questioner quotes in his question is apostolic.
Ministry, since the revelations of God were completed, is no divine standard. The Scriptures, now complete, are. If I need to know the author of an article in order to check that the truth is being ministered, then my standard is not the Scriptures, but a list of humanly accredited servants. No! I must judge an article, or an address, not by the author or the speaker, but by the contents of what is written or spoken using the Holy Scriptures as the yardstick. Who today could say to another: “Knowing of whom thou hast learnt them”? It would make divinely unaccredited ministry the peer of Scripture. An author has every right to hide his identity so that he may be lost sight of because the ministry of truth is more important than its minister.