I don't think there was ever a 30i screen. GP probably meant 60 interlaced, which needs two full scans for a change, so an effective 30 full frames per second,

I don't think there was ever a 30i screen. GP probably meant 60 interlaced, which needs two full scans for a change, so an effective 30 full frames per second, but enough for 60 half images. For a Wayland compositor and the entire hardware stack would treat it as 30hz only if it really wanted to avoid interlace artifacts, but I don't recall that being a configuration that existed in my lifetime.