The term is demeaning to employees, but the connotation is pretty well understood. It's not really meant to convey proper ownership, just that the employee was lured away.

This is probably the correct interpretation. "Poaching" seems to be the word used when a person is specifically targeted because of their experience. They're viewed as key, so it's not just good for the one hiring them, but bad for the company losing them. If you think of hiring as dragging a net through the water an sifting through the catch, poaching would be more like spear fishing.

Or it could just be sensational headline writing.

In a way, your employer does own something: rights to the output of your labor.

People can't even bring themselves to use the distinction for Waymo/Uber and Levandowski.