It is all Covid-19, in the same way that all dogs are dogs. But if we're trying to teach software to recognize dogs visually, the more breeds (and the more different the breeds) involved, the more likely it is the software will miss some. That software is our immune system.I think we are looking at this through two different lenses.
To me it is all the same thing (Covid-19). You see each variant an a separate entity.
I am not nearly smart enough about things like viruses to be that objective.