The AF - at least what Sigma claims - is changed to the needs of mirrorless. So it's a bit more than just a fixed spacer, but if I were Sigma I would go the same path: The lenses already are big, heavy and good. More distance to the sensor is a good thing in terms of corner vignetting, I think. Developing a new set of lenses, although there is no FF mirrorless from the big 2 would appear to me as economical bullshit, sorry. If samyang wants to dedicate themselves to Sony bodies, have fun - they already are new kid in town if it comes to AF lenses, so why not start with what it's available.
But Sigma's hesitation I understand fully.
But Sigma's hesitation I understand fully.