"This is problematic for skewed data"
I agree, this is a common issue in data analysis, the mean is sensitive to outliers (or, asymetric distributions more generally) and therefore it makes sense to also calculate the median, which we do. It is also possible in openLCA to export all simulation data and perform more analyses, e.g. related to an assumed distribution, with this data. I do not think, though, that there is a right or wrong, correct or incorrect, here, as often in data analysis, but of course the arithmetical mean is not perfect, as other indicators too.