OK so replace the Photoshop example with a compiled GIMP or shareware binary. It doesn't change the fact that it is not open source.
The free software community complains all the time about binary blobs that are otherwise legal to freely distribute. Like firmwares. But somehow this is all overlooked with these "open weight" models.
I'm not at all disagreeing with you about calling these models "open source". They mostly aren't and we should stop conflating the two things.
I agree with you in general, it's not "Open Source". But in many cases you're allowed to fork them, and create and distribute derivative works (finetunes) from open models, and the training and inference code is also permissively licensed. That's not shareware.
And working with the binary weights of a huge pretained model is much easier and cheaper than doing it based on the entirety of its humongous source datasets.
Lord forbid open source models have as horrible a user interface as GIMP!