Per the OSD definition of source code, "the source code must be the preferred form in which a programmer would modify the program." which means an argument could be made (as charcircuit is making) that the weights, being the preferred form to modify, are the source.

I do prefer open weights as being more precise (like, is it even really software that has source code in the first place?) but I feel like at this point the ship has sailed somewhat (though if this is something you're willing to spend your time arguing then... moral support I guess?)