Let's stop saying that open weight models are open source. They are just a software that you can run on your own hardware (if you have a ton of money to spend to get it anyway) but they are not open, they are as open as any proprietary software that you can run on your PC is.
You can't study them, you can't modify them, you can't improve them, you can't look into how they are built etc.
You can't study them, you can't modify them, you can't improve them, you can't look into how they are built etc.