I would argue that the weights are as much source code as source code. Them being generated doesn't demote them.

I don't even think the distinction is important. The "system" should be open, and that includes data central to the system's operation within certain bounds.

You can open source parts of a system at whichever fine slice you wish, you just have the part which is open A and the part which isn't B.

It's the value of A and B being open that matters, not what A and B are composed of.