I admit, I did not click your bartolini link! You're of course correct that there are other designs that would allow coil splitting with humcancelling between standard single and both split-humbucker-sides. Another idea would be to have a custom dual coil made where both coils under the hood are traditional jazz pickup coils, but in the same polarity, so both are rprw with the separate standard jazz pickup coil in the other position, then they just wouldn't cancel hum between each other in dual-coil mode.
I saw the "neck pickup" being duscussed between the OP and you in those earlier posts, but I was thinking specifically about the doublecoil in the bridge position, since the OP's issue was that he accidentally had the bridge pickup in the 70s position