It's a grey area, it depends a bit on what you did in that week, if its just general framework/setupwork I see little difference between that and using say the Godot XR Template. I think many jammers will take something they have already build as a base or copy stuff from existing projects to save time.
If you had been working on something for months and decided to reskin it to the theme, that would be a clear violation.
But after only a week, even if it is "half finished", unless you had prior knowledge of what the theme would be I don't really have a problem with it. Especially seeing that right now our jam is just for fun. If we had prices up for grab I might be taking a closer look at what "half finished" meant :)