Two viruses may be possible, but other diseases certainly can have similar ranges of problems: The Flu might case different type of lung problems-- pneumonia, bronchitis, exacerbate asthma. Or it might hit your stomach, or result in ear infections by allowing other opportunistic infections to fester, or seizures. It may cause pericarditis or other heart problems, or strokes. So it is not unreasonable to assume that Covid-19 might cause the same symptoms through 2 different mechanisms.