Having access to a weight doesn't make it open. Else you can make the argument that Microsoft Word is open source because you have access to the binary.
The model is a static data file like a word doc.
Meta open sourced the code to run inference on the model (ie the code for Microsoft word reading a doc file).
They also open sourced the code to train/fine tune the model. (Ie the code for Microsoft word writing a doc file)
Then they released a special doc (the llama 3 model), but didn’t include the script they used to create that doc.