I bought a used OM-1 a while ago, and it's slowly turned into my favoured camera for video since then (despite some of its annoyances).
I think part of the reason for that is because it has a very fast readout stacked sensor, with rolling shutter time around 5-7 ms in FHD & UHD, which seems to give a 'solidity' to the video combined with fluid motion handling (I normally shoot at 50p), compared to my G9 with about 12-15 ms rolling shutter.
If my liking of the OM-1 video is due to low rolling shutter then maybe I'm subconsciously sensitive to the picture distortions created by rolling shutter (including interactions with the IBIS behaviour). But then I'm often filming subjects like trains which readily show up rolling shutter distortions, so maybe that's sensitised me to it?