BTW (as I noted in the bug description): I tried again some days ago and I noticed a similar linked bug when underexposing:

It should be correctly that way that at ISO 100, 200 or 400 the picture is expected to appear slightly darker step by step when the exposure correction is set to -0,5, -1,0, -1,5, -2,0 (underexpose).

But this is not working correctly as well: At ISO 100, 200 or 400 the picture changes to a very dark exposure (almost black) when exposure correction it set to -0,5, -1,0, -1,5, -2,0 (underexpose).

This linked bug wasn't noticed before because it is not easy to notice that the darkening of the picture is much to overdone instead of going darker slightly step by step.