and I agree that installing linux as a binary makes sense. but people didn't think it was important to maintain the reference back to the actual source used. I think to some extent (RedHat specifically), the patch sets used and the hidden build process was used to make it less trivial to reproduce.
apt source htop
apt build-dep htop
cd htop-2.0.2
dpkg-buildpackage -us -uc -ncSeriously, this is nit picking, and you seem to acknowledge that here by using the term "less trivial". Instead of "tar -x" you run "rpmbuild -bp" to get the patched source RedHat will unleash the compiler on. For debian its "dpkg-source -x". I'm not even sure that it could be called "less trivial".
Getting hold of the source in the first place it looks to be "more trivial" to me as there is no Wumpus hunt to find the URL. For Debian it's just "apt-get source package-name". The RedHat equivalent is "yumdownloader --source". In both cases that gets you the exact source used to build the binary on your machine. I don't know what you would call a strong reference back to the actual source used, but I'm struggling to see how it could be much stronger.
As for the "hidden build process": it's only hidden because it's automated. You may as well be blaming "make" for hiding the kernel build process, which is more complex than most distro package builds. But every step the distro build processes (any distro) can be made very visible, naturally enough because otherwise it would be impossible to debug when things go wrong. And there is excellent doco on how to do all of this for both Red Hat and Debian.