Injecting a substance that kills or sufficiently stalls the Virus would classify as a "treatment".
The definition of treatment you are using is narrow to the point of being false.
Definition of medical treatment Medical treatment means the management and care of a patient to combat disease or disorder. Medical treatment includes: All treatment not otherwise excluded (below). Using prescription medications, [...]
www.wisconsin.edu
"Medical treatment means the management and care of a patient to combat disease or disorder."
Drugs are only one of many possible forms of treatment.
In the case of COVID-19, the primary treatments are supplemental oxygen and/or mechanical ventilation and they are very effective treatments.
Oxygen and ventilation also are not "only treating the symptoms". COVID-19 kills by inhibiting respiration and anything that increases respiratory efficiency is a treatment of that. It does not need to attack the pathogen directly to treat the disease. The pathogen is not the disease. Asymptomatic infected have the virus, but have no resulting disorder or dysfunction, and thus no disease.
This may seem nitpicky, but it's not. If you are dying of COVID-19, your are almost certainly dying of pneumonia and if you attack the SARS-CoV-2 virus in the late stages, but do nothing else, you're still going to die.