It seems to me that there is a big difference between 'vintage' and 'vintage reproduction'.
Enfields have a continuity of production that starts from Britain and goes on to India, with British influence even in the early days of the Indian factory. First it was an assembly plant in India, then parts were actually made there.
I am well familiar with both furniture reproduction and boat reproduction, and, in these, shortcuts are often made because the original skills just aren't there. I talked with a furniture restorer from England who did work for Southby's. Well, a hutch of some sort was sold as original, but when he dissembled it, he found that plywood was used, so it was a reproduction, though Southby's sold it as an original. I asked the restorer if he informed the people who had bought it that it was a copy. He said no, he was being paid by Southbys. No, it definitely wasn't vintage furniture, but a rather modern reproduction.
In this regard, R E India didn't pull a rabbit out of a hat in producing the Enfield line - there is a continuous heritage, so, in my book, it is a true Enfield, and to that extent vintage. Vintage does imply age, like vintage wine, so, when the later R Es get to old age, they will be true vintage, they will have aged.
Various Japanese companies make retro bikes that look like old Harleys or Indians, the Kawa w650 is a triumph look-alike, but all are of up to date technology. They are modern bikes with a vintage appeal.
Now the question arises about the UCE and no, I would say, it is not vintage any longer because of a severe break with tradition. A bit like using plywood in an old appearing piece of furniture. But this is arguable. On the other hand, the AVL is a continuation of the tradition. My bike still has the 4-speed transmission to prove it.