Well, the input profile does have an influence on the matching, although for luminance only (what is done here) it’s probably not big. However, I see your point, so I’ll think about how to put it in the exposure tool.
Do you expect this to work in interactive mode only, or should this be something that goes into a pp3 or which can be applied in batch mode? If the latter, we would have to think about how to do it properly, to avoid having the same usability issues that the current “auto levels” has (i.e. if you have a tone curve set, the results are way off).