Actually, the boats in your pictures are very close to being double-ended as are boats with overhangs.
Not trying to be argumentative, but I'm not sure many people would consider Cornell's Ovni, or Beth & Evans' Samoa, as "close to being double-ended"... :-)
True canoe stern hulls are an older idea but there are still plenty of them around. They used to be and still are the choice of many long distance sailors regardless of what a few "name brand" sailors may use. They have advantages and disadvantages. Actually, the boats in your pictures are very close to being double-ended as are boats with overhangs. The main advantage is to allow a following sea to slip by in the same manner the bow lets water slip by with minimum alteration in direction. The stern buoyancy theory is probably true to a point but once breaking waves get high enough to hit all that glass, the stern will get pushed around more than in a boat with less exposed surface area. That doesn't seem like rocket science.
You're right, of course, there are still some voyagers out there sailing double-ended boats (Eric Forsyth is among the most prominent that comes to my mind), but I think their numbers continue to diminish... With the demise of Valiant, I can't think of a production builder that continues to produce double-enders. (Pacific Seacraft technically might qualify, if they were actually still building boats in any numbers)...
I have a bit of experience with double-ended/canoe stern boats, one of my all-time favorites was the Alden 38 SEAFLOWER which I ran between Maine and Florida numerous times:
But much of my time offshore has been with the Valiant 42, an absolutely wonderful all-around boat...However, when confronted with a breaking sea of a height sufficient to break against a transom, those boats are just as vulnerable to being pooped as any comparably sized yacht with a reverse transom... And, one of the primary purposes of a drogue, in addition to limiting speed, is to inhibit the stern from being "pushed around" by a potential wave strike...