In this case you just can't spin it any other way than it being a derivative work of Blender. And this is great.

My understanding is that the LLM stripped away the non-UI code from Blender. The majority of the code is ported directly from GPL'd code from the Blender code base.

It depends on what you're building. If your app is free software, a GPL library is no problem at all. (and your own code can even stay MIT or Apache.)

It "cannot be considered" only for proprietary apps.

You can work around that. If you have an application that also has a command-line option, then you could create a UI for that application with this library. The UI module for your application will have to be under GPL because this library is licensed under GPL. But your core program can still be closed-source, as long as you distribute both parts separately. A bit convoluted, but I've seen some applications that do this - they don't distribute the GPL code directly, but ask you to download it separately. (In fact, if I remember right, they had done the opposite of what we are discussing - the developer had created a closed source UI for an open source GPL application, and asked the users to install the open source application through Linux package managers). As far as my understanding of the license goes, this conforms to the GPL only if (1) the GPL code isn't essential or a core part of the application, and (2) you don't distribute both as one application (which implies that the GPL part is absolutely necessary part of your application, thus violating the first rule).