At the moment (work on Whonix 10 in progress) there is a discrepancy with Whonix's apt repository. Currently packages are Whonix 10ish. Any fixes for Whonix 9 are difficult to test. Those packages have naturally lower version numbers. So people who just want to help testing the small fixes so they can migrate into the stable repository, don't really want or should use the testers repository, because that comes with a lot more changes. The only solution I can see so far is introducing a forth, stable-fixes-testers repository. Then we'd have:
If you can think of a better solution or got a better suggestion for the name as alternative to stable-fixes-testers, I am all ears.