Nothing about the original Greek in that verse implies "learning" or "taking in knowledge." There is nothing to substantiate a rendering of "taking in." Even the Kingdom Interlinear Translation (KIT) has as literal translation "they may be knowing" which does not indicate an overt action of "learning" God and Jesus. To add that, the translators had to insert words that the Greek text did not contain.
Now, the translators may have reasoned that no one can know something they have not been taught. But as many Christians can anecdotally attest, the teacher is not necessarily a human or a book.
Basic to this text is the very notion of gnosis, "knowledge," and its identification with "eternal life" (i.e., not "knowledge that leads to everlasting life" but "knowledge which is eternal life"). This points to the early gnostic mindset, where "knowledge" is not doctrine (contrary to the WT "accurate knowledge") but esoterical illumination, intimate recognition of one's divine origin.
The extant text of John 17:3 has very likely been designed to suit the orthodox (or even, according to some, Jewish-Christian) pattern. About halfway is 1 John 5:20:
we know that the Son of God has come and has given us understanding so that we may know him who is true; and we are in him who is true, in his Son Jesus Christ. He is the true God and eternal life.
Btw, this illustrates the quite complex trajectory of the Revealer figure (Jesus-Christ) in Johannine texts; identified to God in 1 John 5:20; separated again from God in John 17:3.
