Well, I appreciate you explaining where you're coming from with the 1-2-3-4 EB vs 1-2-3-4 DB. I agree that when one goes EB to DB the left hand needs to be strengthened, the lack of frets requires more accuracy and pressure, and being a vertical rather than horizontal orientation for the left arm, any movement will have to be re-learned.
For most of us DB players who have spent a long time playing 1-2-4, myself included, the concept of having a 5th between fingers 2 and 4, and a minor 6th between 1 and 4, is bizarre. So much of what we do when playing is a combination of muscle memory of shapes and patterns in the left hand. When playing, we don't think about where a 5th is, we
know it, and have to know it on a subconscious level. Without it being rooted way down in the subconscious we are playing bass using our conscious minds, and there's only so much room in there!
While completely relearning the shapes and patterns when doing a 1-2-3-4 EB to 1-2-4 DB change is very possible - especially considering how different the instruments feel physically for the LH - it takes time. Being able to use the same
fundamental hand shape, retaining the 2-4 perfect fifth, and the 1-4 perfect sixth, speeds the process to this subconscious hand-shape Nirvana, and this could indeed be a factor in considering searching for a one-finger-per-fret DB teacher when coming from EB.
I don't think I've ever heard anyone say, "I wanted to play DB because I love playing 1 finger per fret", but if the same fingering system exists and works well, then why not, right?
New concepts for double bass fingerings aren't approved by any worldwide governing body. There isn't any laboratories conducting tests on monkeys playing 1/112th size basses. (I hope.) The 'proof' of if it 'works' for the wider community is in the
playing, and those videos I posted earlier show 1-2-3-4 DB working really well. I don't appreciate the term zealot, considering that I don't use the system. Especially when its coming from a 1-2-4 zealot like yourself. (joke

)
I don't think there is any one way to play the double bass. Just a really interesting spectrum of methods and techniques that can be blended to form an individual's technique. At the moment (I imagine) 99% of double bassists use 1-2-4, (or 1-3-4.) If Silvio Dalla Torre is correct, and the 1-2-3-4 method is the method of the future, then why not consider it when coming from EB, and keep some of the fundamental concepts?