Seems this version is primarily for some Olympus cameras. On these models the pseudo-mirror box interfered with mounting the Speedbooster, so Metabones removed some features to slim it down enough to fit.
Support O-M10, O-M1 and O-M5, also Panasonic GH4, GH3, GH2, GH1 cameras and BMPCC without jog-dail button. Not support external power supply ( Not support BMCC).
Appears the only current camera the Speedbooster "S" isn't practical for is a BMCC with a passive m4/3 mount & only when used with lenses that feature electronic focus &/or aperture.