In the article,
"The OM-1 appears to automatically detect the focal length of adapted manual focus vintage lenses. It doesn’t have the usual entry in the menus to add a focal length for a non-CPU lens like on Panasonic, Sony or Nikon cameras. At least I haven’t found it."
It does not automatically detect the focal length, and if it is set to compensate for a much longer focal length than what you have mounted, it will actively blur your images/footage, rather than stabilize them. There are a couple of ways to set the focal length, either quickly from the IS settings, or by creating a lens profile and switching to it, so that the name and maximum aperture of the lens you are using will be added to the EXIF data.
"The gain in aperture is significant too, an F1.2 lens turns into an F0.76."
As per the Metabones website, "with a maximum output aperture of f/0.80 when an f/1.2 lens is used."
https://www.metabones.com/products/details/mb_spef-m43-bt3
