New review comment by paper42 on void-packages repository

https://github.com/void-linux/void-packages/pull/42687#discussion_r1133053200

Comment:
It's a simple expression and it's only used in one place, when someone not familiar with the template reads it, it's not immediately obvious what $_version is, but it would be obvious if the expression was directly in $distfiles.
I am not sure how having separate $_version makes this more maintainable for you, could you explain that?