They do it when the person is no longer a flight {wander off} risk to make more availability on a secure unit for new patients who can wander off. They also do it when medical condition requires a more skilled level of care medical wise.
My sister was in an assisted living memory care unit for over two years. She was a high flight risk and had to be in a secure facility at the time. After two years her disease {Dementia} had progressed to where I thought she needed a nursing home so they could restrain her to prevent falls as frequent as three a day. I got her into a nursing home I trusted {I'm a former employee of several of them} and she lived another year but did not try to wander off from there.
Thanks for that info. I hadn’t thought/realized they could reach a point where the wandering tapered off, much less thought about the increased need for medical care. Learn something new every day. What a complex world our health care system involves, with so many variations on each and every ailment. I hope it can survive the coming years.