There's a philosophy of open source based on recipients being able to make any small and large modifications to the source material as they see fit.
Just being able to build new projects with something or read what it does not qualify in that context -- it requires the freedom to rework the thing itself to suit your own needs and ends.
In the case of these models, that philosophy would have the source training data and the training algorithms themselves available, editable, verifiable, and repeatable. Ignoring the financial challenges, a truly open source model would let you remove, add, edit, or reclassify a sample in the original training data and then build new weights of their won.
The released weights are not that kind of open source, and that's what these arguments are generally making the a case for.
There are still plenty of grounds from which to critique that argument if you wanted to, but there's no straw man involved in it.