I think I know why Luke 22:44 is phrased the way it is. It's kind of an odd phrasing, because we know from D&C 19 that it actually was blood, so why is it phrased in Luke as a simile? Let me preface the explanation by noting what appears to be a Hebrew idiom in 1 Nephi 8:4, Alma 36:22, and 1 Nephi 1:8: "Methought I saw..." Lehi clearly had a vision, but perhaps he is unsure, like Paul in 2 Cor 12:2, whether he was in the body or out of it in this experience, and it appears to me that the wording expresses this uncertainty as to whether this spiritual vision counts as what he calls "seeing." For all I know this idiom is in the Old Testament too, but if so it isn't translated the same way.
Jesus says in D&C 19, "Which suffering caused myself, even God, the greatest of all, to tremble because of pain, and to bleed at every pore, and to suffer both body and spirit." Luke records, "And being in an agony he prayed more earnestly, and his sweat was as it were great drops of blood falling to the ground." Here's what's happening. Jesus sweats blood in his agony. Elder Talmage notes in his book that this is extremely unusual, and would kill a normal man. Luke is not an eyewitness, but the apostles were, and some of them may have seen what looked like blood coming from Jesus' flesh during the process. Neither Luke nor the apostles knew for sure what had actually happened because Jesus didn't discuss it with them, before or after his resurrection, and so Luke is uncertain what the substance actually was. Note that this is a minor physical detail not recorded in any of the other gospels. And so the situation stood until March 1830, when Jesus saw fit to elaborate upon his experience in the revelation to Martin Harris.
"The presentation or 'gift' of the Holy Ghost simply confers upon a man the right to receive at any time, when he is worthy of it and desires it, the power and light of truth of the Holy Ghost, although he may often be left to his own spirit and judgment." --Joseph F. Smith (manual, p. 69)
Be pretty if you are,
Be witty if you can,
But be cheerful if it kills you.