SAR isn't exclusive to trail areas. They search in town, too. They train for dementia searches. Around here, you can't qualify for SAR without that training.
Ending a search after 4 days wouldn't be unusual at all; in many cases, SAR can have determined that the case is a recovery and not a rescue. They may have determined that continuing is too risky for members, at least at the moment. Algorithms are used to determine probabilities of a successful search, as well as the experience of the SAR lead, and the risk to SAR members.
From articles/LE statements ^^^^, it's clear the dementia was not mild, and JA unfortunately had a history of getting lost. She had been retired from her job as a pastor because of the dementia.
Although JA might have made it off the trail, there's no "safely" that goes along with that possibility, unfortunately. There are lakes, busy roads, complicated streets, no food, cold at night and not dressed for it....not to mention, more trails.