My Colony version: 0.69.0
OS:Android (8.0.0)
Mobile Device: Samsung Galaxy S8
So I've been able to recreate this effect a couple times now but when you are building a structure like the investment bank or something else that requires the drone or turbo drone and then queue up tall housing (anything that requires drones) immediately afterwards my unemployment will spike. My first time encountering this I had about 3k unemployed colonists when it happened and when I recreated it the second time it was just over 300. I've attached screenshots to show it. And if you look in the picture you can my last encounter with this as the little up tick in unemployment before my current one. Far left on the bar is a fire drill so disregard that.
I'm not sure if this is an intended feature for the colonists to be actively looking for better jobs but if that's how it works then it will be good information to have.