In Debian unstable, many of the packages are submitted from upstreams (eg. the folks that made the software.) The bar is simply "Debian developer" uploads the package, as I understand it. The Debian developer may or may not be the upstream source.

In Debian testing and stable, you're getting software that has been through a longer and involved peer review process by Debian maintainers. That's not ridiculous, that's why you would use a stable distro in the first place. Because it doesn't put so much trust in upstream vendors to always put out consistently good production-quality releases without adding any new bugs in them.

I don't recommend using stable distros for anything but production machines, and those you keep to approximate them (like say, staging machines).