I think the reason that Tennant's comments appear potentially contradictory is that the appearance of the length of the nail at rest is not the same at rest as when striking a note. Although the free margin of the nail may appear to extend beyond the tip at rest, it turns out that when the soft tissue is compressed against the nail as it is when the finger crosses a string to strike a note, the end of the flesh and the edge of the nail line up. I don't think there's any contradiction in that at all.
The FEELING of a non-overhanging nail is what to strive for. It will FEEL like there's no overhang to the nail while playing (no "catch" or delay in the note, warmer rather than brighter tone) while at rest there will be a small visible amount of nail extension. The "ramp" shape is useful because the string compresses the flesh in a straight line or plane and the flat ramp supports all of it across the contact patch. The unfortunate problem is that not all the fingers contact the strings at the same angles, and the same finger will be at different angles at different times.
"If I have seen further it is by standing on the shoulders of giants." -Sir Isaac Newton
Armin Hanika 56PF