I wasn't involved in the work mentioned in the post, but I worked on integrating QEMU into oss-fuzz.
Here's an example of a report from oss-fuzz, that we get by email:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=29225
This lets us download the test-case and reproduce the bug, locally.
Internally, we convert this test-case into something that can be used with an unmodified build of qemu, for developers unfamiliar with oss-fuzz, and post it to our own issue tracker:
https://gitlab.com/qemu-project/qemu/-/issues/450