Didn’t they just move the code that was previously executed in the proprietary kernel module to the new also proprietary userspace driver
Probably. And that is exactly what was expected from them since the beginning of their Linux drivers. Kernel is not a place for such big and proprietary piece of code. So this is the important change.
Yes, the driver is still proprietary, but it does not break the kernel any more the way it did.
Non-toxic glue would be starch or gelatine - both used as base of some ‘real glues’, both with valid culinary use, including exactly this use case. We just don’t call those ‘glue’ in this context.