Empirically 5/10 is average.
This is why numbered scores are rubbish. People shouldn't be considering what these scales are that's empirical.
6/10 does seem harsh for what I've played of H5 though but that's s different point.
Do you even understand what empirical means?
Empirical means that if you take all the publications with a 10 point grading scale and you average them, you get a 5. It clearly isn't.