A possibility is that some might be briefly admitted for observation, if they are symptomatic and high risk. High risk cardiac patients get admitted all the time based on symotoms and medical history alone for "rule out" , which usually takes about 24-48 hours. Same with likely transient ischemic attacks.
Insurance companies generally put down somewhat strict admission and length of stay criteria, depending on the diagnosis. If the admission doesn't meet the criteria, then the hospital often eats the cost. I haven't worked as a hospitalist since before the pandemic, so I don't know how well defined the criteria for COVID are, but it is possible that if the standards are still evolving, their might be a little more leeway for a hospital to admit a patient under "out of an abundance of caution" standards. Most of these patients would probably get discharged fairly quickly.