it is not really possible to determine when mutation in a haplogroup happened...
they as everybody else just use some supposed models based on ad-hoc parameters... there is no way to verify such models and assumptions about parameters...
Can you provide some source which explains what you are saying about mutation rate?
I agree that reliability is not 100%, but disregarding this kind of analysis is very wrong. In fact genetic researchers always give range for their age calculations, precisely because they know that 100% accuracy is not possible.
Basically what you are saying is that all they are doing is useless. In that case you should not write on genetics forum, but you should offer you "name similarity" theories on some science-fiction forum.