At the moment (work on Whonix `10` in progress) there is a discrepancy with Whonix's apt repository. Currently packages are Whonix `10`ish. 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.