Are you suggesting that you should enable the employee to move work done on company time and that is the company’s IP to a new company?
And the new company would also be liable for using trade secrets that they shouldn’t.
And the new company would also be liable for using trade secrets that they shouldn’t.
However I do write 1-2 hour PoCs on my spare time and my own equipment, using only publicly available stuff - they sometimes come handy at some point later. If we assume 'remote first' development is okay - with no possibility to test stuff locally, well, we're back to either bookmark managers or pet projects to keep at least a bit of knowledge between jobs.