Your point is fair in the sense that the research cited in OP establishes a correlation between these symptoms and SARS-CoV-2 infection. The cited research does not claim causation. Indeed there are many confounding factors such as pre-existing chronic conditions that were not controlled for in the study.
That said, you're probably getting some down votes because it's well established in the scientific literature that COVID-19 encompasses all of these symptoms.
That said, you're probably getting some down votes because it's well established in the scientific literature that COVID-19 encompasses all of these symptoms.