To be fair, if all you want is a package with Debian you can do that too. Just copy files in to a dir(like package() in your Arch example), write a 10 line DEBIAN/control in there(like the preamble in your Arch example), and call "dpkg-deb --build". The linked document is describing something different, joeyh has a short "why?"¹ from years ago that may be helpful.
What is different in OP that makes that approach not suitable? The git upstream? In the AUR example I gave, pkgver() auto-updates $pkgver, which will show up in version control. You can run `makepkg -defo` (or -dfo I forget which rn) to just run pkgver().
Or use FPM and ignore all the official rules. It will still work. https://github.com/jordansissel/fpm