If you don't understand how ExpSim works, that does not count as a ML bug. If LiveView refreshes 30 (or 60?) times per second, how can it have the same brightness as a 1/6-second exposure? Obviously, by bumping ISO to astronomical values.
This is why I said so many times that you should not record video in photo mode (and nobody believed me).
Only in movie mode, the exposure values displayed on the screen are the same values used for silent pics.
And even there, the downsampling process (line skipping) increases the noise, compared to a regular picture. Plus, you were comparing a raw to a jpeg (raw unprocessed and jpeg with noise reduction applied).