Well, I like to be able to download the source with wget or nix-prefetch-url with a single cut and paste.
Also the code is shorter and cleaner this way.
It is true that the version number is repeated twice, but I find it a minor annoyance.
Anyway, in this case is a "mirror://" link, so it doesn't make a real difference.
I just added a commit to reintroduce the version variable.
I don't have a strong opinion on this point.