If I shorten the focal length of a lens without taking further action, it will reduce the flange distance required for focusing to infinity – which means that if the actual flange distance is not changed, the focus will be closer than infinity.
Is this effect used to get an internal focus on the main lenses, and does this explain why the effective focal length decreases instead of increasing in such designs when it is focused more near?
In other words, do these lenses focus breathe BECAUSE you focus them, or do they focus breathe TO focus?
DO NOT ask questions about real cine lenses or ultra-large floating elements here.
(NB, although this may seem like a question of pure optical design not related to photography, it can become relevant when evaluating the best way to choose or modify lens adapters).