Unlike a copyright where copyright springs into existence at the moment the work is fixed in a tangible medium of expression, getting a patent is a long, drawn out, and formal process.
If you do something on the job and get a patent for your employer as part of the job, you'll know exactly who owns the patent before the patent application is even filed (your employer will be the owner 99.9% of the time barring weird exceptions). Your employment contract will spell this out in detail, and on top of that you'll also be signing an assingment agreement around the time the patent is filed, which is an agreement to assign all rights to future patents that arise from the application to your employer. This is all very formal, spelled out in black & white, and leaves little room for error assuming a minimal level of competency. In other words: In the real world, this isn't a problem and as usual there is an academic proposing solutions for a problem that doesn't actually exist because it's more fun than trying to tackle real problems, which are harder to deal with.