Source code is, for the GPL, the “preferred form for modification”. Given the outrageous cost of training from scratch, plus the ability to fine tune models... I don't think it's completely ridiculous.
Edit: plus, the industry acts like models aren't derivative works of the training data. If true the source license is less important than the model!
not so much about reading/modifying the source, more about what you can build on top, but point taken, could use a different word, "public domain" would be nice if anyone actually wanted to give something back to the public after digesting all the information ever produced