FESCo discussed this today. The ultimate decision was to keep both KDE and GNOME on aarch64 as release blocking, but formally agree that responsibility for ensuring test coverage and investigating aarch64-specific failures now lies with the KDE team (for the KDE case) and @jlinton (for the GNOME/Workstation case).
We (quality team) will retain responsibility for maintaining openQA and expanding openQA coverage on ARM (I’m currently working on this), and openQA will provide results for a lot of the tests. But responsibility for required testing that is not done by openQA lies with the folks mentioned above, and they also need to help out with investigating and resolving test failures.