Correct, there's no global timeline, so it's not clear what "just" 300M years ago even means. Some RFs seen it already, and some will never see it. But in ours it happened in Jun 2024. It's 300M light years away, not ago.
Due to this relative motion we will see different ordering of events at different locations, despite both being at rest relative to the CMW background, so we can’t really say there is a global timeline.
The thing is that the CMW background isn’t global, we don’t see the same background as a distant observer. CMW photons that are passing us now will take time to reach a distant observer, and vice versa.