If I may interject, some morphs have a visible het. Though some may argue, pieds have a visible het and it is even more pronounced when combined with some codoms. At least with the line I have been working with, I can pick out hets from 50% and 66% clutches. So far my picks have proven in all cases.
I do agree the percentage of possibility should be fully disclosed. I think the use of 50% het and 66% het is only because of the assumption of common knowledge of the terms and meanings.