I would like to see the link to this journalist. I assume they were looking at just one hospital (we know that testing, admissions, and ICU utilization vary widely by facility and over time). Less than 20% of inpatient admissions in a typical hospital are surgery patients, and it's been declining for years as more and more surgery is done on an outpatient basis. The majority of surgery patients come directly from home to pre-op, go to the OR, then PACU/post-op and then home, or are admitted overnight for observation. Only the sickest / more complex procedures are typically admitted for more than 24 hours.
And I've worked in half a dozen hospitals (5 acute care and 1 psych) in the central Kentucky area, and I know there are empty rooms, even whole wings/floors that are not used. But I think you mean available beds not rooms. No, hospitals don't always keep 100% of their beds full. Here is a link to a site using HHS data that lets you see percent of inpatient capacity, ICU use, and Covid admissions for hospitals around the country (just select the state and region)
Hospital Capacity and Covid-19
Also, beds and capacity are different things. Capacity requires beds, staffing, and equipment / supplies. Covid-19 patients are more staff intensive, require use of PPE that isn't used with most patients, and may require interventions like proning and ventilator assisted breathing.