The multi aspect part of the GH1 and GH2 sensors was actually that they were wider than normal m4/3 sensors, which meant less of a crop factor when shooting 16:9 video (I think the sensor was actually about 18.8mm wide instead of the usual 17.3mm or so, that's why people wished the 3 and 4 were 'multi-aspect' too. The GH2 never shot good 4:3 video, there was a hack to boost the dimensions/bitrate of the 4:3 SD MPEG mode, but it looked pretty bad and was 30p only.
The GH4 is the only camera that has a high quality 4:3 mode, but even that actually has less FOV then a GH1 or GH2 shooting in 16:9 (since the 4k modes are pixel for pixel crops).
This is all to the best of my knowledge, would be happy to be proven wrong.
Also, fingers crossed that the GH5 will use the whole sensor area for any 4K 4:3 mode it may have.
Thanks Ryan,
That explains it well.
Cheers.
